Migrant workers' theater ripens after 20 years.

``Our weapons were poetry and song, not clubs,'' says Luis Valdez, founder and artistic director of El Teatro Campesino, the ``Farm Worker's Theater,'' a revolutionary Mexican-American company born 20 years ago on flatbed trucks in the sun-baked fields of the Delano grape strike. ``When you have a dangerous situation -- where people are being beaten, killed, exploited, you have to speak out as strongly as you can. . . . We improvised on the spot,'' remembers Mr. Valdez, who created short ``actos,'' or scenarios that dramatized the plight of the farm workers. Workers themselves performed the skits in the fields and along picket lines to instruct and recruit. Later, the show was toured nationwide to garner support for the grape boycott. At the end of the st ruggle, Cesar Chavez's United Farm Workers of America was born, and El Teatro Campesino had won an Obie award.

Now based in the peaceful historic village of San Juan Bautista in northern California, the company has toured Europe six times and won three Los Angeles Drama Critics' Circle Awards and an Emmy. Valdez's 1978 production of ``Zoot Suit,'' based on the controversial 1942 ``Sleepy Lagoon'' murder case, was an explosive amalgam of music, dance, and drama that ran in Los Angeles for 46 weeks. It featured Edward James Olmos, current star of TV's ``Miami Vice,'' in an electrifying personification of the mythi cal Hispanic figure ``El Pachuco.'' A run on Broadway and a film version followed. Last year, ``Corridos,'' an evening of traditional Mexican ballads, toured to San Francisco, San Diego, and Los Angeles.

``Political theater has to do with people's self-determination,'' Valdez continues. ``There is a new racial diversity in America. A new perception of what it means to be American is afoot in the land. It's invaluable -- not only for Hispanics, but for blacks, Asians, the northern Europeans -- everybody will benefit.''

To get his messages across, Valdez employs a variety of traditional and innovative theatrical techniques. ``When I was with the San Francisco Mime Troupe,'' he recalls, ``I learned about commedia dell' arte, improvisation, movement, taking the classics and adapting them. This experience served as the background for my work in Delano. It made it possible for me to do things without props, without lights, without a stage. I learned to perform in the parks, so I knew I could perform in the farm fields. Of course, I also had a familiarity with the work of Brecht and the social-conscious theater of the 1930s, such as the `Living Newspaper.' ''

The Teatro's work shows traces of all of these influences, as well as Valdez's own creativity. A short, stocky man with a resounding bass voice and vibrant brown eyes, Valdez is a magnetic performer as well as a writer and director. Born to migrant farm workers in Delano, he began picking crops at the age of six. By the time he was 12 he was producing puppet shows. After graduating from San Jose State College in 1964, he went to San Francisco to get his plays produced. ``But I found that it was difficul t,'' he says. ``I needed Chicano actors for the Chicano roles -- there were no Chicano actors, no Chicano directors, no Chicano theater -- period.''

After spending a year with the San Francisco Mime Troupe, Valdez joined the Delano strike effort and created Chicano theater he'd been seeking. ``Before the strike I had a vague notion I wanted to start a company,'' he says. ``I had no real sense of what it would take to pull it together, but I had an inward feeling the most important ingredient would be the willingness of people to perform. I found that with the people involved in the grape strike.''

Today the theater's scope has broadened. ``We mean to reach everybody,'' says Valdez, ``not just Chicanos. We try to reveal the basic humanity in everyone. I think there is so much in the human being that we haven't discovered.''

In celebration of its 20th anniversary, El Teatro is presenting three of Valdez's early plays. In July, the company performed ``Soldado Razo'' and ``Dark Root of a Scream'' at the Latino American Theatre Festival at Joseph Papp's Public Theater in New York, and ``Bernabe'' will go on tour this winter. At a Nov. 9 awards dinner in San Francisco, the group will formally announce the establishment of a collection of the works of Valdez and El Teatro Campesino in the archives of the University of California

at Santa Barbara.

A new comedy by Valdez, ``I Don't Need to Show You No Stinking Badges'' (the title is a line from John Huston's classic ``Treasure of the Sierra Madre''), will open in San Juan Bautista in October and will play at the new Los Angeles Theatre Center next spring. A film he wrote -- and will direct -- ``Viego Gringo,'' based on a novel by Carlos Fuentes, stars Jane Fonda and is scheduled for 1986. With his brother Daniel, Valdez is currently working on a screenplay for ``The Richie Valens Story .''

``One of our goals is to create performances that will remain as literature,'' says Valdez, who encourages new Chicano playwrights. ``What's most important is what remains on the page -- either as music or as words. Then these works can be created again and again. You can influence generations to come by what you write.''

Although many of the company's performances are in large cities, Valdez stresses the importance of the group's ties to the ``campesino.'' ``What the Teatro Campesino still emphasizes is that attachment to people of the earth,'' he says. ``I think that many of the problems in our cities today come from the erosion of traditional country values, such as family, the neighborhood, being able to communicate with other people instead of feeling like a stranger. The urban areas need contact with the rural area s to maintain their humanity. People come here to San Juan Bautista from the cities on weekends to refresh themselves, to reconnect.''

The theater's headquarters are in a renovated fruit warehouse in this picturesque community. Shows are developed and presented here before going on tour. Every Christmas El Teatro performs a Mexican folk play in the town's nearly 200-year-old mission. This year it will be ``La Pastorela'' (``Shepherd's Play''). Flat-bed productions

The original ``actos'' were simple, sparse skits illustrating the injustices suffered by the farm workers. Music, mime, and a commedia dell'arte style of comedy were employed; sometimes printed signs were hung around the necks of performers to clarify meanings.

In one skit, one actor was labeled ``grape,'' another ``older grape,'' and another ``raisin,'' to make the point that, if workers stayed out on strike long enough, the employer's precious grape crops would turn to raisins. Although the workers were amateur actors, under Luis Valdez's direction they gave energetic, credible performances.

Years later, when ``Zoot Suit'' opened in Los Angeles, the company had acquired polish and professionalism, but it retained the strong attack, raw energy, and exuberance that had characterized those early, primitive ``actos.'' Dance music from the 1940s enlivened the production, and actors strutted across the stage in the slithering, almost horizontal walk of the ``Zoot Suiters. Interspersed in the dialogue of the mostly English production were words and phrases in both Spanish and the Anglo-Hispani c slang of the period. Hispanic members of the audience would sometimes burst into laughter at dialogue inexplicable to the Anglos -- a phenomenon that added to both the flavor of the production and the fun of the evening.

``Corridos'' was a vibrant evening of music, song, and dance expressed in the hundred-year-old tradition of the ``corrido,'' or Mexican folk ballad. Although not specifically a political piece, it had the same driving vitality of Valdez's earlier works, and its underlying message reaffirmed the dignity of the common man. ``We have always spoken to and supported the spirit within people,'' says Valdez of the evolution of his company. ``If people are overcome with bitterness, hatred, and suffering, th ey cannot accomplish things. Now our approach is more sophisticated, but the spirit is still the essence of it.''