I assume you are staying in the beach area or the Conch Republic end. You do not want to drive in that end of the island a lot. Parking is expensive. Buy all day tram tickets ( hop on and off) or rent a golf cart for the day to get around. Walk as much as you can. Hemingway, Truman Whitehouse if you like history. Pub crawl at night, people watch in the day. Mallory Square ( This is where sunset happens)and Duval Street and the marina area all walkable. Stay on the beach when the cruise ships are in. Pick up a good tourist brochure and find what you are interested in. Some of the museums are really good with stories of old Key West. Have Fun.