As Phil says there has been a lot of discussion worth searching on.
Short version: I would rent a car and explore if you want DIY, otherwise jump on a flats boat with a guide and take some shots.
DIY - explore Islamorada's public access spots around Matecumbe, then down to Pine Key / Bahia Honda State Park area (camping if you call way ahead). Bahia Honda - go mornings and evenings, walk out 100 ft from shore and watch for tails between you and shore. Very exciting stuff, I got an 8# there many moons ago.
Boat rentals at Bud and Mary's among other places. Fresh grilled yellowtail snapper, conch chowder and an authentic key lime pie for dessert.
IFFF Certified THCI @ 2005
Capeflyfisher Guide Service
Island Hopper, Guitarist, Incurable Dreamer
and Founder, Worldwide Flyfishing Forum