Hangers are like fishing spots in the Keys. Nobody gives them up. Call Marathon General Aviation FBO and ask if they have space in there hanger. It will cost you some bucks. My RV stays on the ramp. I have a good Bruce canopy cover I keep on it. KMTH overnight fee is 15 dollars a night. They have both truck and self service fuel. They will shuttle you for free locally to restaurants or hotels. You can get a car at the FBO for 40 dollars a day or check on line for car rental prices at Marathon airport. The FBO will shuttle you to the terminal and sometimes you can do better on rental pricing on line. Its an hour drive from KMTH to Key West, but a great drive. Most scenic part of driving the keys. The Marathon FBO folks are great. They bend over backwards for you. At Key West, if your not burning jet A, you got nothing coming. Tight ramp space and not so caring ramp ops.