X2 forJolly Roger, in fact we are there this week. They honor Passport America for up to five nights,which pays for the membership in one night. Their price is fair even at full rate. There are seasonals but plenty of short stay folks.
Full hookups, cable TV, dog friendly, large laundromat, new pool and restrooms in recent years. Most sites have mature trees and other tropical plantings. Nice Gulf side dock for watching sunset. If they had a little bar and grill on site, I'd love it even more, but Grassy Key is at the north end of Marathon, so plenty of restaurants and grocery stores close by.
The summer rate quoted in their literature is $60 a night.
Love all the state parks in the Keys but so does the rest of North America. Tough to get a reservation from the minute bookings open 11 months out, except during October maybe. Sometimes you can pick up a cancellation or just show up and luck out.