Below is a copied discussion from the Net's "Ask Your Neighbor" page, which, in turn was copied from the AGLCA list.
This discussion contains a lot of truth, and a lot of good advice. Too bad though that Captains Joe and Mary Beth didn't read the posting below about the new dinghy dock on Tarpon Basin. That would be a good alternative.

Is there any dock that is available in the Keys to pick up a passenger without major charges? Are there any public accesses that can be used to bring a dingy without substantial charges? I feel that we must be the first to come to the Florida Keys on a limited budget.
We have enjoyed lovely anchorages and much appreciated free mooring balls. The state and national parks are beautiful. However getting to shore to enjoy the communities seems to be a challenge. Access for those with mobility impairments is especially difficult.
Since coming to the Keys we have found charges for each bag of trash placed in a dumpster and for filling water tanks. If those charges are modest it certainly is not a problem. However, renting a marina slip seems required to gain access to land. We are spending enough time that we do not always need to buy more fuel so our access to marina docks are limited.
Any suggestions on useful access points would be appreciated.
Eddy
aboard Seldom's Escape

We have found the mooring fields in Florida to be incredible, and not that expensive.  We stayed two months in Marathon at City Marina, and have stayed at Key West Mooring field before, and now after our trip to the Dry Tortugas.  Secure dingy docks, free pump outs, and good transportation (buses).
Just my .02, YMMV
Joe & Mary Beth Amelia

You have found the problem for transients in the Keys. Land is precious, landing opportunities are mostly at the cuts where the water is deeper.  Municipalities are not oriented to transient services.
Marathon is the big exception and Plantation also has a good municipal marina.
If you just want to pick someone up I would give a call to a likely spot and get their reply.  Plantation Yacht Harbor on the bay side will let you do a touch and go I believe.
We live at Key Biscayne which is north of the Keys proper but you can land at Crandon Marina and No Name Harbor.  You cannot linger at the marinas of course because they have to keep customer access.
Greg and Susan Han