I've sailed the area that you're referring to aboard my 26 footer. She has a 3'2" shoal draft keel
. I think you'll be fine sailing a boat with 5' of draft as long as you pay close attention to your charts
.There are a lot of shallow areas all through the Keys, but it's a great area to sail, and isn't difficult if you use a little caution.The "creeks" that go from the Bay side, to the ocean need to be considered carefully. Some drop down to ~2' at low tide.I met a fellow cruiser at a place called "Pumpkin Key", close to Key Largo
. His boat drew 5' and he didn't have any problems sailing the area. Good luck!