Getting a big island overview makes it nice for conversation when you are sipping on the papa doble cocktail. Stay busy all day on the tours and the reef boat trips. You learn so much, this tour makes sense for your second day on the island. Do the trolley tour and Rent a Scooter on the first day to get a good feel for the big picture. Save your walking for the evenings when on Duval with drink in hand. As you move on to later days, start drilling down to all of the neat local things and educational tours.
Expect to have an excellent time on the touring train around the island. I wish the prices were little bit lower. People should be able to jump on, and get off where ever they want all day long. I wish this went completely around every major part of the island, it has a big focus on Old Town Key West. I assume they can't make money if it goes all the way around past the Airport and down roosevelt boulevard. If it did the complete perimeter around the island, people would be glad to use it as transportation to get into the action. They do a very good job on every part of it as it is fun. The running commentary that the person driving the train gives you is excellent and well thought out. We were very excited to get on it and it did not disappoint. It is well worth the money, but would be even better at about 25 percent cheaper.