The spectacle of Cuba wracked by economic difficulties and suddenly abandoned by 100,000 of its people has struck many Central Americans and Mexicans like a dream come untrue.

Conservatives, for whom Cuba has long conjured nightmares, are openly gloating. Moderates are disturbed and puzzled.Admirers of Fidel Castro's revolution -- though they cling to their admiration -- have been forced onto the defensive.

An instant cliche heard all over the area is the description of Cuba as a paradise lost. A Social Democratic leader in Costa Rica, Oscar Arias of the National Liberation Party, says flatly that, "for the first time in the last two decades Castro has had a setback. It [Cuba] looked like a paradise and now we see that it is not."

A conservative television commentator in Guatemala showed pictures of the suffering crowds huddled behind the fence of the Peruvian Embassy in April and declared "this is the paradise the Marxists have been promising."

In the face of such reports and propaganda even a communist member of Costa Rica's Legislative Assembly is willing to concede that the favorable impression of Cuba "has been diminished in some uninformed sectors" of the population outside his party.

By and large, Castro's popularity among leftist and revolutionary groups in Central America has little to do with the nature of his government. gRather, it is based on his successful defiance of the United States.

The recent exodus has tarnished but not destroyed Cuba's image. If respect for Castro has declined somewhat, the essential qualities that he was seen to represent before are still respected by many leftists, revolutionaries and their followers in this area. If there is a weakening of popular support for Havana it does not necessarily mean the currents of leftist insurrection sweeping through this part of the world will lose any of their force.

One member of El Salvador's revolutionary movement, for instance, said privately that "now we see after 20 years there are serious problems in Cuba. It has made us think the Cuban revolution is not our revolution. But we have not been imitating them anyway. We are learning from the Cuban situation and also the Nicaraguan. It's just another experience you have to take into account."

In Nicaragua, the more conservative groups have used the Cuban crisis to lambast the leftist revolutionary Sandinista government. Many of the Sandinista leaders have spent considerable time in Cuba and feel strong sympathies for Castro's regime. The debate still rages, but earlier this week it was announced that Castro would attend the July 19 celebration of the Sandinistas' first year in power. The public reception he receives may be some indication of how average Nicaraguans perceive his actions over the last few months.

In Mexico, the government has a tradition of following a fairly conservative line at home while applauding revolutionary movement abroad. One diplomat has suggested that the Mexican foreign minister has "almost a romantic conception" of the Cuban revolution.

Less than two weeks after the Cuban crisis began with the occupation of the Peruvian Embassy in Havana by more than 10,000 people seeking to leave the country, even such Mexican intellectuals as former Communist author Octavio Paz were talking about Cubans "voting with their feet" against Castro's government. And at the same time Mexican President Jose Lopez Portillo announced he would make a state visit to Cuba at the end of July.

Uno Mas Uno, an influential leftist newspaper in Mexico City, hailed Lopez Portillo's decision as "a dignified and efficient act of solidarity in the face of the propaganda campaign against Cuba."

In a region which has always feared and often felt the heavy hand of U.S. intervention, Castro's Cuba is the only country that has successfully turned its back on the United States. That the end result has been acceptance of massive Soviet influence and dependence on Soviet aid is seen as less important to Castro's admirers. Identification with Cuba's revolution, in its simplest terms, is often seen as identification with independence from the United States.

As Daniel Ortega, a Sandinista member of the Nivaraguan junta, said recently, "We [in Central America] have never felt the weight of Soviet imperialism. We have experienced United States imperialism many times."

After at first losing the initiative, many left-wing politicians and publications in this area have made a comeback in recent weeks with defenses of Castro's regime that suggest the flight from his island is no fault of his but of the general phenomenon of underdevelopment.

Castro is in some cases praised for being more humane than other communist leaders because he allowed the dissidents in his country to leave rather than confining them. Arguing somewhat the other side of the coin Castro's defenders also suggest he was smart to get rid of so many undesirable people.

A headline in Nicaragua's Sandinista newspaper, Barricala, over a story about riots by the new Cuban immigrants in the United States, said, in effect, "Fidel Told The U.S. They Were Scum."