Hello From Fleet 111,
Mary's right, if your looking to camp in the keys American Outdoors is a good place. You'll have to moore your boat in the water, look for a break in the sea wall and rocks to the south there is a spot you can pull the cat out of the water. Avoid the popular weekends, i.e. Memorial Day, the Keys in general are over run with people and boaters. We've also found over the years some very reasonable motels that don't mind the cat. Check out Bay Harbor and Rock Reef (a little more money but you get a larger beach for the boat).
The best time to go is May, not to hot and generally consistent weather. In fact, our group is there every year the week before Memorial Day weekend with cats and powerboats. We've stayed all over the place down there and found Bay Harbor, Rock Reef and America Outdoors to be the best place. The water out back is absolutely fantastic and the sailing is awesome. Check our website for contact info if you'd like more information.
www.fleet111.com