If Orlando (ie. theme parks) doesn't float your boat ... take the opportunity from Miami (which you should spend a day or two in, SoBe, etc) to go
- North, via Fort Lauderdale (nice spot), up the coast to Cape Canaveral, awesome place to visit if your interested in big machines (and even if the other half is not!)
- South, down the Keys to Key West, not my favourite, but you have to do it at least once for the experience and the sunsets, etc. Book a hotel on the keys half way or so and chill for a day and way the keys beachs (out a mile or so) or scuba. Its quieter somewhat up the keys and cheaper than KW which is an obvious tourist trap.
- West, my favourite is to head due west from Miami, down Alligator Alley (100 mile straight drag) to the west coast and Marco Island, Naples, Fort Myers, Sannibel Island, etc. Bit quieter, chilled, bigger houses, some great sites and coast.
Otherwise, from a biking point of view the area is pretty crap in a lot of places, flat, boring roads, few bends. Great for a cruiser (HD) but pretty boring that far south otherwise.
HTH, have fun ...