There are no trails to the Keys. You have forests in the north part of the state and Ocala National Forest in the central. To get to the Keys you are going to have to shoot across Alligator Alley from Naples on the West Coast to Homestead behind Miami or down 27 in the center of the state, 95 or 1 on the coast. No trails just lots of people. If you plan to camp in the Keys you better have reservations and be prepped for tropical camping. No-see-Ums go right thru regular tent screening, they are going to give you a whole new outlook on life. The State Parks in it Keys are Pennekamp in Largo, Curry Hammock in N. Marathon and Bahia Honda right after the 7 Mile Bridge south of Marathon are usually booked up to a year in advance, watch for cancellations on Reserve America every day. Right now is Hurricane season so be prepared for cancellations and evacuations, IMO not exactly the best time to be camping in Fl. the mosquitos will be so bad in the Glades you won’t be able to get out of your truck. Safe travels.
