Where should I go on my vacation?

I am planning a trip to a tropical location most likely around May 2012. It will be my present to myself for my 21st birthday which will be in January due to college I will not be going until May when I get out. My boyfriend and I will be going but neither of us have ever went anywhere by ourselves we have always had family with us. Also neither of us have been on a tropical vacation. I am trying to figure out where to go so I can start figuring out the approximate pricing and everything. However, I can not for the life of me decide where to go. I am the type of person who LOVES doing things on vacations like my number one thing to do is swim with dolphins. I also want to go snorkeling but I also want to do other fun things I normally would not be able to do. Where should I go? Of course, I want beautiful beaches and all that. Should I go to hawaii, jamaica, the bahamas, aruba, mexico, dominican republic. Please any suggestions would be great ! (: