Old San Juan, Puerto Rico. Antique shops, delightful caribbean paintings, colorful downtown. If you dare (windy mountain road, Puerto Rican drivers behind you :), drive to the Areceibo radiotelescope -- it's amazing!
Puerto Rico! Spent practically every summer there as a child and teen (perhaps even a few as an adult)! There were many advantages to having a Puerto Rican mom (aside from eating delicious food every day of the week)!