anything that looks good. Just make sure it does not have any bugs. when I bring home wood from Mexico I put it in a plastic bag for transport and then I rebag it and put it in the freezer for a few days to make sure nothing lives to enter my world..
You do know that there are pen turners at the US Customs at the border? Right?? If you can get past them without your timber being confiscated follow Cindy's advise and freeze any of the little suckers that may be in the wood. Heck, even microwave them bugs just to be sure.
I always have double bagged and then when home boiled anything I brought back from any of my many excursions to the West Indies, Bahamas, etc. (It was great being a licensed diving instructor. The perks were always great as well!) and often there are quite a few 'surprises' that floated out. Those that refused to swim for it are ultimately boiled inside the wood and that makes for an even bigger surprise depending on how big a bug they 'were!'
Hope you have a blast on the beach down there. Just watch your backside as things are getting hot in certain areas. You do watch the news, right?