Not sure if this is what you saw or not, but we have seen them on the pier where the ship docks. They will take you up and down the pier, between the ship and street/mall area, which is quite a long walk, especially in the hot sun. We used one in 2013 and at that time there was not a set fee, they just worked for tips. Our 3 kids were pretty young at the time and after a long excursion, they were so tired of walking. Not sure if they have them anywhere else in town.
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