We enjoy the Florida Keys, but prefer to move around as opposed to spending a month in one place. Great anchorages abound. Swing into a marina every few days to top off water, pump out the potty, take a long shower, and find good places to dine out. Due to crappy weather the winter we were there, we did spend more time in Boot Key Harbor than any other single place... mooring balls, showers at the marina, washers/dryers (some even work), and a weekly pump out. Marathon is centrally located in the Keys, so it's easy to go either direction, depending on the weather.
Good Keys cruising guide:
http://www.managingthewaterway.com/guid ... eys-detail
That guide tells you about the places on land as well as where the good anchorages are, etc, etc.
Even though it is way south, be sure to bring cold weather clothes - we found January in the Keys to be down right chilly the year we were there. Oh, there were glorious days, too (don't get me wrong)... but, when a norther would blow in, you will want a good source of heat and a warm jacket (preferably Gore-Tex®).
Oh, and a sense of humor. Some folks in the Keys enjoy being different. George (C-Dory Traveler) taught us the term: Keysie (not just a decorating theme, but more of an attitude).
Have a great time and keep us posted.
Best wishes,
Jim B.