Oh really?
Two words for you: Hugo Chavez...
Please keep your political paradigms straight---Hugo Chavez is not a communist. He was freely elected in internationally monitored national elections in 1998---while he does have socialist views, this is not synonomous with communism.
As far as Cuba goes, the fact of the matter is that the ONLY reason why the United States maintains an embargo on Cuba is that the Cuban political lobby is the second-strongest of all the international lobbiest groups (Israel being first), and it would be political suicide for any president, Democrat or Republican, to lift it. All the more so in the case of George W, who needs to get his brother re-elected.
Fidel Castro is an impotent old has-been in the twilight of both his life and his political career. It's high time for the United States government to begin a policy of economic and political engagement with Cuba in so that the transition to a free and prosperous nation is hastened.