See my thread Ascencion Bay Bonefish Flies (
http://www.ifish.net/board/showthread.php?t=146129 ) THe fly selection is about spot on. I'd have sme streamers, some crazy charlies, some gotcha's adn a bunch of smallish crab patterns. Make sure you have some that are weighted, some heavily, some medium, and some light. Also have a few unweighted flies. The good news is, the Keys have a lot of great fly shops, so you can go buy a few flies and get soem real advice from the real on scene experts.
Good luck and post pictures!