When the Presidents of 20 Latin American countries gather in Guadalajara, Mexico, on July 16 to commemorate the 500th anniversary of Columbus' voyage, one leader will stand out as particularly desperate: Cuba's Fidel Castro. As his Soviet patrons retrench, Castro must seek financial salvation from his Latin American neighbors. But they'll exact a price. After all, they don't want to be pitted against the gringos just when they're all seeking free-trade deals with the U. S. While on stage, the leaders will give speeches on how Christopher Columbus got them where they are today and will pay homage to Spain's King Juan Carlos and Portugal's President Mario Soares. Behind the scenes, they'll lobby the increasingly isolated Cuban to cut out his inflammatory rhetoric and liberalize his regime.