nacho, go to yahoo and search for virgin islands forum. lots of choices. the only thing i can tell you about san juan is to get ready for the airport. it's laid out wierd and you have to walk forever.
AND, if you like usvi, you'll LOVE the bvi. same amazing water, but very, very laid back...always on island time. not as touristy as usvi. you should be able to take a ferry over to tortola and the little islands.
the bvi is my favorite.