Jamaicans Face Clear Choice at Polls. Large turnout likely as voters weigh conservative leader and socialist-minded opponent. CARIBBEAN VOTE

ONE recent night, youths from central Kingston, a slum-ridden area where political tension has traditionally run high, staged a dance for young supporters of Jamaica's two volatile political parties. ``You wouldn't have seen this in 1980,'' said organizer Dunston Whittingham, as attendees danced to a pounding reggae beat. ``You would have seen them shooting each other.''

The campaign for Jamaica's general election tomorrow is proving a far more peaceful affair than the 1980 vote, which left hundreds dead.

In fact, conservative Prime Minister Edward Seaga and his opponent, the socialist-oriented Michael Manley, have signed a peace pact and have repeatedly urged their supporters to refrain from fighting.

Like Mr. Seaga, who has spent eight years building tourism into this tropical island's No. 1 money-earner, Mr. Manley says he understands the need for Jamaica to avoid the negative publicity it earned in 1980.

``Everything we hope for in Jamaica is on the line at this time,'' Manley said at a recent news conference. ``Tourism is going to get all the attention we can give.''

Under Manley's two terms as prime minister in the 1970s, Jamaica saw a steady decline in economic growth - a result of his ``democratic socialism'' philosophy and close ties to Cuba's Fidel Castro, which drove away investors and many of the island's professionals.

Still, today, Manley is leading in public opinion polls by 13 points over Seaga.

``Despite the hardships of the 1970s, the voters remember a [Manley] government that was very active in trying to improve their situation,'' says Carl Stone, a political science professor at the University of the West Indies, explaining Manley's appeal.

``In contrast, Mr. Seaga's structural adjustment policies have drastically reduced the role of government as a provider of benefits for the poorer classes,'' Professor Stone says.

The election is attracting close attention from US officials. To the Reagan administration, Jamaica under Seaga was a key friend and a showcase for free-enterprise in a region seen as susceptible to communist influences. As the largest English-speaking island in the Caribbean, Jamaica is the foreign-policy bellwether for the basin.

Although Manley's earlier government had strained relations with Washington, US State Department officials who visited recently indicated they were conciliatory to a Manley win.

But sources in the banking industry here say investors are uneasy over the possibility of Manley returning to power. They say one multinational company that does business on the island has booked passage home for its employees for Feb. 10, the day after the election, in case Manley wins.

It is current Prime Minister Seaga who is credited with restoring financial stability to the island nation. His strong dose of capitalism and heavy borrowing to fund a restructuring of the economy appear to have lured investors back.

Unemployment has declined from 26 percent in the early 1980s to just over 18 percent, government statistics say, and exchange rates have held steady for several years.

The restructuring has had a heavy price, though. Jamaica's foreign debt of almost $4.5 billion translates into a high per capita debt for its 2.4 million inhabitants. Still, last September, after Hurricane Gilbert caused havoc across the island, Seaga's close ties with the Western world helped bring in millions of dollars in aid to reconstruct devastated tracts.

The charismatic Manley acknowledges that many of Seaga's programs have worked, and that some of his ideas of the 1970s were mistakes. He seems to have mellowed in his eight years of semi-retirement, spent lecturing abroad and writing books on politics and the popular game of cricket. He has traded in the modified Mao jackets he favored in the 1970s for suits and ties, and says he expects to have excellent relations with US President George Bush and the International Monetary Fund, the nation's largest creditor. Manley had broken off relations with the IMF in 1980.

Despite the changes, Manley's basic philosophy of a people-oriented government that listens to the views of all and keeps secrets from none is intact. Manley is credited with creating a minimum wage, maternity benefits, and free secondary education for the poor.

Although many of the nation's legions of poor consider Seaga cold and uncaring, the Harvard-educated descendant of Middle Eastern immigrants has introduced numerous programs for the elderly, single mothers, and children in his two terms as prime minister.

As a young sociologist, Seaga lived in one of Kingston's worst ghettos. He was reelected in 1983 in an uncontested election.

Seaga has argued that the sorry state of the economy he inherited from Manley made it impossible to improve social services until this year. Last spring, he unveiled a $1.2 billion, five-year program to improve hospitals, roads, and schools.

He has charged Manley's proposed plans are a ``pale imitation'' of his own successful policies.

Voter turnout in Jamaica, a country passionately committed to democracy, often hovers over 90 percent, and election officials say if the atmosphere of relative peace remains then voter turnout Thursday will be one of the highest ever.