Not that it matters in the scheme of things, but to my knowledge Jet Blue only code-shares out of SJU now. They are not true Jet Blue flights. Usually Seabourne or similar.

I'm not sure that I would ASSUME that you could recheck your luggage immediately. Maybe you could, but I wouldn't count on checking it that early. Some places you can only check luggage 4 hours before your flight. I don't know if you could call Jet Blue and they would be able to tell you or not.

Are all 12 people going to want to do the same thing?? What I might have a tendency to do is to get a day room or two, at someplace in El Condado area or at the El San Juan. You could store your luggage and carry-on's there, and then hang out by the pool, etc. for those inclined and the others could go downtown for the more actively inclined. For those that haven't seen it, El Morro is magnificent, as well as the other fort downtown, which I can't think of the name of at the moment. CRS setting in..