I know this thread is old, but had to put in my 0.02 cents about Tampa. Riding on roads sucks in Tampa (this from a runner, not a cyclist, but based on my observations), however, there are lots of bike paths with no car traffic that I hope to use once I finally buy the bike:

Suncoast Trail (41.3 mi one way) http://outdoortravels.com/biking_fl_..._suncoast.html
Pinellas Trail (34 mi one way) http://www.pinellascounty.org/trailgd/
Upper Tampa Bay Trail (8 mi one way) http://outdoortravels.com/biking_fl_...abaytrail.html

There are plans to connect all of the above trails.

There's also Wilderness Park http://outdoortravels.com/biking_fl_...rnesspark.html These trails are great for running too by the way.

There are lots of other areas within driving distance that are good for cycling.