bc,
I too would strongly recommend a guide. There are flats everywhere you look in the Keys.....unfortunately, most are too soft to wade. FFing in the Keys is mainly a boat game. There are some shore/wading spots, PM me and I'll refer to some of them although the ones I'm familiar with are up RT 1 rather than in the immediate KW area.
The good news is is that May is prime time! Many FFers head to the Keys in Dec-March and wind up disappointed as the flats glamor species can be very spotty during the cold months (although there's a ton of other fish available, esp if you're willing to use spin gear). May is during the prime tarpon run (call your guide ASAP as they can get booked up early during the tarpon run). Tackle and rigging is complex and depends on too much to discuss here unless you have very specific questions. Generally, for bonefish you'll want a 8 or 9WT with a disc drag and at least 100 yards of backing. Tarpon are generally fished with 10-12WT rods and 12s are usually recommended for beginners. Permit and a host of other critters can be chased with 9-10WT rods - these include jacks, cudas, snappers, cobia, small sharks, mackerel etc. Floating lines are typical and bonefish flies are generally big and heavy in the Keys.
FFing in the Keys is difficult and I'd recommend you go with an open mind. Even the schools of mangrove snappers ("mangos" as locals call 'em) that swarm under every dock can be hard to feed a fly. If you really want to catch fish, bait and spin gear will open a heckuva lot more opportunities. A guide I'd recommend (I think he still guides out of KW) would be John Smouse. He guided me to my first permit in May 2008.
Good luck.
