Scooters are, in my estimation the best way to get around town. But that may be because I have been riding for more than forty years and I still enjoy it. Having said that I have to accep that riding a motorized two wheeler, even one limited mechanically to 29 miles per hour us not to everyone's taste.
Indeed there is more than one way to enjoy getting around Key West, so why choose a scooter? Well, there are many rental outfits and they will give a helmet if you choose to take one. Please do, and learn how to wear it properly. You won't see many riders wearing helmets but you don't get the 911 calls when they go down and get flown to Miami ($30,000) to get their heads rebuilt at vast expense. Funerals are cheaper all round.
Scooters are useful, easy to park though not on sidewalks please as there is lots of free dedicated parking. You can ride a rental scooter, most of which are limited to 50cc engines on a car license which is actually a bit crazy but legal. You will be in the company of many like minded middle aged "non biker" tourists and residents who view scooters as useful, not as lifestyle accessories. Just try to remember these are vehicles on city streets and you are not in Disneyland, a fantasy place where adventure outcomes are certain and locals are paid to be polite. In Key West pay attention as you ride.
Some people in Key West personalize their rides. You would never mistake this for a rental:
Scooters are practical, useful workhorses, especially in a town that's flat and only four miles long. Stock Island is usually out of bounds for rentals.
But they are also fun, and can bring out the kid in you. The responsible one we hope, but still a kid.