Wow. Isn't it interesting how people have different experiences in the same places.
I arrived in Miami on Lucia, my Wauquiez Pretorian 35, in late 2003 and based myself at the Miami Beach Marina in the heart of South Beach for about 15 months and loved every minute of it. Nice people, good boat services, great night life if you wanted it, and full of people from all over the world. Following some time in the Exumas, I sailed back to my then home port of Sag Harbor, NY. But I really liked and missed Miami and ended up renting an apartment on the water in South Beach for the winter and have essentially never left. I sailed Lucia back from Sag Harbor, to Miami 3 years ago and keep her on a mooring at the Coconut Grove Sailing Club and now live about 1.5 miles from the boat. I have never had a theft problem in three years there, and I leave my safety equipment and winch handles, etc where they belong on board. There has been only one thief in the Club's mooring area (150 boats moored) in three years and that was by a visiting cruiser! My only experience with boat related thief was in Sag Harbor, NY (the Hamptons) where my dinghy with outboard was stolen, not in Miami. (BTW, the Coconut Grove Sailing Club rents guest moorings with 24 hour launch service and showers, etc for visiting cruisers and is walking distance from a good ship's store and "the Grove".)
As to other parts of Florida, I have great experiences a Fernandina (St. Mary's Inlet) both at the town dock and on the hook across from it. It is a lovely little town with very nice people. Port Canaveral works as a good place to check in with customs when returning from the Bahamas on ones way North. Vero Beach is a wonderful and very beautiful place to stop for a while. The city mooring field provides showers and a bus to town and the people are super nice. It is a bit of Connecticut with palm trees, but that's OK too. Anchoring north of Peanut Island at Palm Beach is protected and very pleasant. Lots of cruisers use this as a good place to wait for a weather window before crossing the Stream to the Bahamas. Ft. Lauderdale is all docks, but if a major boat problem has arisen that needs really top flight repair folk, that is " the" place to go south of Annapolis for top flight workmen. Miami I've discussed. A trip down to Key West can be fun. It is a bit of a crazy place, but crazy can be fun and often is.
Additionally it is worth remembering that a lot of what you get is what you give off yourself.