My bike was stolen once, and I have been interested ever since in protecting my bike and finding out as much as I can about this HUGE bike theft problem in Key West.
1. Protect your bike by locking at least your frame and rear wheel to a bike rack. If you use a U lock, you can simply lock the rear wheel to a bike rack through the bikes triangular frame at the wheel (without touching your frame if you want), and it is impossible to steal your rear wheel and/ or frame without either cutting the lock or cutting through the wheel. The smaller the U lock you use, the less leverage the thief has with bolt cutters. Btw, I know one person who locked their bike to a street sign, and the thief just lifted the bike up over the sign to take it. Also, a chain link fence is much easier to cut with bolt cutters than a lock... Make sure you are locking your bike to something truly secure and in such a way that it cannot be ridden away with the lock in place (i.e. lock a wheel to the frame so the wheel cannot turn to ride it).
2. Use at least 2 locks. The heavier the lock, the stronger it is. If you keep your bike outside at night, keep your heaviest lock attached to your night bike rack (the most common time bikes are stolen). Use your lighter lock while you ride around during the day (if you don't want to ride around with the heavy weight), and then use both locks to secure your bike at night. Make sure when you use 2 locks, or 1 if your cable lock is long enough, that you secure both your frame, rear wheel, and front wheel.
The most common parts stolen off of a bike seem to be the bike seat (with or without post) and the wheels. The wheels can be locked to the bike with 1 or 2 locks.
3. You can use a small, inexpensive cable lock to lock your seat to the frame, as most thieves simply remove the seat by hand versus stealing a bike with bolt cutters.
I have heard many people say their bike was stolen from their fenced yard where it was not locked. Please lock your bike wherever it is. These thieves are even breaking into houses sometimes to steal expensive bikes. And your bike is not safe just because it is unique and would be easy to spot. Some stolen bikes are recovered even a few blocks away from where they were stolen as if it was just a temporary ride, but many bikes seem to disappear from the island forever and may end up in other island countries where bicycles are a vital part of the economy as people can travel further on a bicycle for better/ more working opportunities.
4. Don't forget to get a KWPD bike sticker. It is free, and if your stolen bike is floating around out there this will ID it so you can get it back. It will also legally verify the bike is yours. Take a photo of the serial number usually on the bottom of the bike. This can prove to police the bike is yours and is important to be included in a police report. And please do call the police to file a police report if your bike is stolen. Maybe if everyone who had a bike stolen in Key West would contact the police to file a report perhaps the PD would designate a detective in charge especially of the bicycle theft problem. Good luck to all of us bike owners in keeping our bikes!
Updates: Someone told me they had 2 bikes stolen from one of the shorty bike racks (that holds maybe 5 bikes) while they were enjoying their evening - the entire bike rack along with the bikes was stolen and taken away. They were told that a group may be coming down from Miami and just stock piling bikes in Key West into a truck and taking them back. Then, they take their time removing the locks up in Miami. It sounds like we need to lock our bikes to bike racks large enough or permanently secured enough that 2 or 3 guys can't remove the bike rack and carry it off.
Someone tried to steal my bike again, but couldn't break my cable lock. It appears that they tried to break the ends off with perhaps their hands or something blunt, but I've got a really good cable lock with Kevlar reinforcement, so they were only able to break the plastic cover over the ends. I think they gave up when they realized there was yet another, bigger cable they would also have to break through before getting the bike. I googled breaking bike locks and discovered that different locks usually have to be broken in different ways. I am concluding that a good strategy is first to have the beefiest bike locks you can afford, and second that two different kinds of locks - for example one cable and one U-lock or one combo and one padlock - might deter a thief who is prepared to break only one kind of lock. For example, with bolt cutters a thief might not want to try to cut a U-lock and with their hands (or a pen...) they would not touch a padlock and chain.
Also, I tried a bicycle alarm that was less than 7 bucks and do think it is valuable for a bike stored near you such as at your house. Most thieves wouldn't want to handle a screeching alarm when they cut a cable or try to move the bike. I'm sure there is more affordable technology out there in regards to alarms and/ or GPS tracking. Hope this helps.