I am vacationing in Key West right now. Almost the entire length of Hwy 1 (about 150 miles) now has a parallel asphalt bike trail. Most places in the actual town of Key West have designated, well marked bike lanes, as well. Bikes are everywhere. Every place of business has bike racks out front. Obviously, much has changed since the early 1980's! Cycling is huge down here now. I've been practicing riding my old mountain bike in the third highest gear, in anticipation of buying a fixed gear road bike soon. No hills anywhere, but some days, riding into a stiff headwind is a bear in the 21st gear of an old 24 gear Gary Fisher Wahoo! I've seen every type of bike, and every type of rider imaginable in the last two weeks. There are hundreds of loaded tourist bikes on the Hwy 1 bike path. To answer the OP question, you should have absolutely no trouble cycling in Key West, as long as you are talking about commuting and road riding. I frequently see groups of cyclists, and I doubt that they are tourists. Mountain biking however, would be a total bust!