Okay, we are sitting at the cheapest campground in Key West. $13 per night dry camping, $23 per night 50/W/S. But it is on the Naval Air Station, and even in April they expect to be on a FHU/Dry rotation. Have to be military or retired to stay here.
In general in the Keys, campsites are small and close together. You are not expected to be spending your days and evenings around the campfire and picnic table, if you are lucky enough to have one. Camping in the Keys is about the area and other attractions, not the campground.
In the Keys, you have the boonie tax. I.e. everything is more costly. There are some great state parks. I prefer Long Key to Bahia Hondo because RV folks can be on the beach/ water. But sites are hard to get and run $40-50 per day.
Space in the commercial parks will be easier to get in April than this month as snowbirds start leaving.
Check RV Park Reviews and learn about the parks in the lower keys. Then make some phone calls. Don't expect full amenity resorts.
