What are some good places to visit near the Gulf of Mexico?

* Mexico: Cancun, Cozumel, Playa del Carmen, Puerto Vallarta, Acapulco

* United States: Miami Beach, Fort Lauderdale, Clearwater Beach, St Pete Beach, Sanibel Island, South Padre Island, Galveston

* Cuba: Havana, Varadero, Cienfuegos, Trinidad