The trolley was great. You don't have to buy in advance - you can buy tickets right on the pier after you get off the ship. There are several different trolley companies - I did the one with the green cars just this past March - I cant remember the name now. I'm glad we did it. I had heard so much about Key West being a "walking" port where you can walk everywhere, which is sort of true, but you can't walk if you actually want to span the whole island! If you're thinking of going to the southern-most point, especially. Plus, if you're not sure where you do or do not want to stop (like we were), you can listen as they narrate and explain the different areas, and can hop on and hop off at will at the stops that interest you. Its a great means to see the whole island for a first-timer, IMHO.