We spent the first week of June this year in the Keys. My recommendation is that you stay on Marathon Key or one of the other middle keys. Traveling around is a whole lot easier as the drive to Key West could be an hour or more. In season it could be more. There is a lot to see and do all over the Keys. We stayed at Grassy Key a private park and Curry Hammock a State Park. The state parks are the better deal as prices are only around $36, half of that if you are a Fla. resident over 65 or disabled. I had no problem booking for June. Now for snowbird season say Oct to April it will be tough to find a spot in a state park. Private parks will have openings but expect to pay more. Log on Fla. state parks and check out the reservation page and see if any of that works out for you. Remember if you have never been down there a large part of the roadway is two lane and travel sometimes can take a little while and if there is an accident well just be warned. Have fun.