Key West is extremely bike friendly, with most roads having a bike lane, the speed limit is 25 mph, no shortage of places to lock your bike up, the island is very flat (so you can bike with sandals), and the entire island is only a few miles from one side to the other. Laura and Will have rented bikes from this location a few times before, and it was cheap and allowed us to get around for the whole vacation.
Latitudes is one of the top seafood restaurants in the Keys. In order to go to Latitudes for dinner, you will need reservations months out, however you may be able to get a brunch reservation perhaps even the day before. Latitudes is located actually on Sunset Key, and to get there you will have to park in the Margaritaville parking deck and walk over to the ferry location which runs every 15 minutes (free ferry transport with reservation). Don't forget to show your parking stub to the host at Latitudes for them to validate it.
Mallory Square at sunset is a MUST SEE when visiting Key West. Everyone on the island converges here nightly at for the sunset celebration where you can get a piña colada from a street vendor and watch the local street performers. It's positioned perfectly next to many restaurants and bars, so after sunset you can easily go enjoy Key West nightlife.
Fort Zachary Taylor is a beautiful location to see some of the history behind Key West. The brick fort is definitely worth seeing, as all the cannons are still there. There is a large beach for swimming and snorkeling and the happy couple highly recommend biking or driving there for the day.
If you even remotely like coffee, then plan to stop at one of the Cuban Coffee Queen locations for an authentic Cuban café con leche with can sugar. This location is right by the marina, so you can grab a coffee and sit on one of the benches at the marina to drink it.
Southernmost beach is very small, however there are a couple beach bars on the beach like Southernmost Beach Cafe (happy hour 4-6 every day) and you can find delicious food as well at Seaside cafe. It's also right next to the Southernmost Point of the US, so make sure to take a picture with the landmark.
Laura and Will take any opportunity to jump on a boat and go deep sea fishing to spend a sunny vacation morning. They have done charters in Key West and definitely suggest going fishing if you can take a morning to do so. Afterwards, take your catches to Hogfish Grill to get blackened/fried fish tacos, they are delicious! If you are driving through the Keys and want to go fishing, however, it's widely suggested to go in Key Marathon, as that's the best fishing in the keys.
John Pennekamp has some of the most beautiful snorkeling sights you can see without leaving the US. Laura and Will have snorkeled here and seen eagle rays, dozens of barracuda, parrotfish, sea urchins, and all kinds of other sea life.
The Rain Barrel Sculpture Gallery in Islamorada is an assortment of many stores with local art (glass blowing, paintings, photography) and beachwear, but most notably is the home to Betsy the 30 foot tall lobster. At least stop here on your drive for a photo with Betsy.
The Turtle Hospital is an active turtle rehabilitation hospital where they rescue, rehab, and release turtles. You can take a guided 90 min tour on any half hour from 9am - 4pm to see how they help turtles, and feed turtles at the end of the tour.
Sunset Grille & Raw Bar is a great place to stop for lunch for some tasty fish. Don't forget to wear your swimsuit here as they have a large pool. A perfect view of the sunset if you're staying in Marathon, and a great view of the 7 mile bridge.
No Name Pub is a great place to stop for lunch on the way to Key West. The food is delicious, and the dollar bills stapled to the walls are quite a sight to see. Laura and Will have seen some friendly Key Deer around here as well, and hope you get to see one too!