I would highly recommend a trolley tour for Key West. We were there in 2003 so I do not remember all of the details or the price but we loved it.
It was a narrated tour, very interesting and informative. We were able to get off and on at any spot we found interesting. I guess we had a pass to present, don't remember. It was easily walkable to the start of the trolley tour from the pier. I think we paid about $20-25 and doing it on own was cheaper than doing the formal excursion booked though Celebrity.
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