Mexicans speak out against government corruption

''Corruption is Mexico's No. 1 problem,'' says the editor of Contenido, one of Mexico City's popular magazines.

Although many do not go that far, some figures from Mexico's political right and left agree that corruption is pervasive here - and that it is so out of control as to present the single biggest threat to the stability of Mexico and its government.

Contenido editor Armando Ayala Anguiano, whose publication has taken on corruption as its prime editorial target, sees an opportunity this year to begin to correct this unpleasant aspect of Mexico's political scene:

''Mexico has a unique opportunity at this stage in history to choose a new course as Mr. de la Madrid becomes president,'' he says, referring to the scheduled Dec. 1 inauguration of Miguel de la Madrid Hurtado.

It is common knowledge here that many in power enrich themselves during their terms as president, Cabinet officers, and legislators. Mexico's current President, Jose Lopez Portillo, has been tarred in the press for allegedly taking millions of dollars out of the country. Some Mexicans believe he is using government funds to build a complex at the edge of the city for himself and his family.

Rumors of such enrichment have seldom been accompanied by solid evidence. But evidence may be mounting. Consider the following:

* A Mexico City resident named Jose Lopez Portillo purchased a luxury condominium for an unspecified amount in an affluent suburb of San Diego, Calif. , on May 7, 1981.

* Check No. 108 drawn on the account of Guillermo Lopez Portillo at the Capital Bank in Miami for $250,000, and dated Oct. 18, 1979, was made payable to ''Miami International Depts.'' for what, according to the memo line, was a ''purchase of home in Miami.''

* The family of Mexico's President Jose Lopez Portillo is building a five-house complex, the largest a 20-room mansion, on a 7.5 acre compound in the hilly suburbs overlooking Mexico City. Rumor has it that government workers have been used in the project.

* Mexico City police chief Arturo Durazo Moreno is building a mansion-style home near the Mexican Pacific resort town of Zihuatanejo. The home - replete with marble bathrooms, elaborate kitchen, and fountains and statues - is built on land the government gave to peasants to farm.

The police chief's home, as well as the Lopez Portillo family compound overlooking Mexico City, was brought up in the leftist weekly Proceso in an article entitled ''Three Disturbing Mansions.''

The third of the mansions in the article is located in New Canaan, Conn., and allegedly owned by Mexico City Mayor Carlos Hank Gonzalez. The mayor was not known to be a rich man when he took the mayor's job. But the home in New Canaan, which city officials say he owns, is worth several hundred thousand dollars. There is no definite proof that Hank Gonzalez owns the New Canaan home, but it is stirring considerable controversy.

President Lopez Portillo has been silent on the allegations surrounding his own activities and those of his family.

There is no evidence that the purchaser of the condominium in Vista, Calif., - one Jose Lopez Portillo - was the President. After all, the name is fairly common - there being 36 Lopez Portillos in the Mexico City phone book and other Lopez Portillos throughout the country. Still the coincidence is there.

And there is no law against Mexicans owning property abroad. However, President Lopez Portillo has publicly frowned on the practice.

''They should return this money,'' the President said in a recent speech that attacked Mexicans who have engaged in the practice he terms sacadolares - taking dollars out of Mexico.

As for the Miami check written by a Guillermo Lopez Portillo, the relative of the President with the same name denies he wrote it. But photo copies of the check, circulating here, show what appears to be the President's relative's signature. Moreover, sources close to the Lopez Portillo family say Guillermo does have a home in Miami, purchased in 1979.

The Lopez Portillo family compound is another matter. Other presidents have built such structures as they got ready to leave office, with little comment, only some rumor, and few cries for investigation.

But today in Mexico there is a growing demand for greater accountability from its politicians.

The reports of purchases cited here - along with hundreds of other stories of Mexican politicians and businessmen buying up property in the United States and enriching themselves enough to put up mansions - are causing wide concern here. The political climate is different now than it used to be, and subjects such as the building of a family compound by an incumbent president are no longer taboo.

''What we are seeing is a veritable Watergate explosion of investigative journalism,'' comments a source close to President-elect de la Madrid. ''Better that it comes to the surface now than later.''

The Mexican newspaper El Universal has stated that the current economic traumas facing Mexico, together with the start of a new administration two months hence, make this a very auspicious moment to ''at long last confront corruption head on.''

President Lopez Portillo has said nothing about the allegations surrounding his family. Yet on Sept. 1, when he attacked those who had taken their money out of Mexico to invest in US real estate, those in the audience, many of them politicians, applauded.

San Diego County record keepers say that a fifth of recent real estate transactions are with Mexican businessmen and politicians, and that a tenth of the transactions and tax payments are with individuals using Mexico City addresses. One of the names on their records is Roberto de La Madrid Romandia (no relation to the President-elect), governor of the state of Baja California. He and his family purchased three large pieces of property in the San Diego area in 1981.

''That is only the tip of the iceberg of political and business purchases for personal use in the United States,'' says a US real estate agent who sells property to Mexicans.