Culebra Island, Puerto Rico hands down.
http://www.islaculebra.com/ Not very far from St. Thomas (take a water taxi) and DIRT cheap compared to the most other Caribbean options. You can rent a house for what hotel rooms cost at most resorts. Plus, being able to jump on a water taxi and go to the USVI or take an air taxi back to San Juan if you wanna tour the city. Another bonus is the rain forests... Considering you are in FL- I don't think you can get a cheaper flight. Its typically sub-$200 for a flight and here's a bunch of houses for rent:
http://www.vrbo.com/vacation-rentals...culebra-island
If you're looking to get butt naked in a hot tub and do the whole romance thing... can't beat it
