Lake San Marino, Wiggins Pass Road, North Naples might be a place to take a look at.
Its an easy bike ride to Wiggins Pass State Beach and Barefoot Beach. There is ton of activities at the park. 60 to 80 bicycle riders leave the park in small groups for a organized destination ride every Tuesday and Thursday. You are grouped by the speed you want to ride at. 10-12 mph, 12-14 mph, 14-16 mph and 16 mph plus.
There is plenty at this park to keep you busy. The people in the park are very friendly and would welcome you right into the organized and non-organized activities.
A couple of cons- It is expensive compared to other places farther north, but not compared to what they get in other campgrounds in Naples. Most sites are 30 amps and are relatively small.
Good luck with your search.
Paul
EDIT- I reread your post. The nearest grocery store, Publics is about 1.7 miles away depending on your location in the campground. If you do not have transportation besides a bicycle, look real carefully at the campgrounds location, as distance can be very deceiving in Florida. What appears to be around the corner on Google maps is really 10 miles away in some rural areas of Florida.
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