We took the City View Hop On/Hop Off Trolley and found it to be wonderful. The trolley went all around the island and we saw so much of Key West. The hop on/hop off option worked out well for us we never had to wait more than 10 minutes or so for another trolley to come around and pick us up if we decided to hop off and explore. The tour guides were excellent, funny and so knowledgeable. We enjoyed being able to stop at Hemingways house, though the $13 we paid to get in was a little steep for what we got, I thought. It was cool to see the original Margaritaville along Duval Street! I wanted to get a picture of Mile 0/Southernmost Point and was able to get both without having to walk great distances.
We did the Tiki Beach excursion. The bus driver who drove us the quick (about 10 minutes or less) distance to the beach gave great information about the island. We were greeted with a free welcome drink (they had alcoholic and non-alocholic punch available). We were given a free beach chair and an umbrella. They had beach equipment for sale as well as available to rent ($10 for a snorkel/fins for an hour to rent). The beach is not huge, and is quite rocky, but it is beautiful. We had a great view of the two Carnival ships that were anchored off the coast. We also got to snorkel on a reef that was very close to the shore - it was a once in a lifetime experience. I would recommend the Tiki Beach excursion for anyone who likes to lounge in a beach chair and wants to experience some great (cheap!) snorkeling!
We did the Sky Explorer excursion. You can ride up/down Mystic Mountain as many times as you'd like, which is nice...it is really truly beautiful. At the top of the mountain, there is a small nature museum, a few vendors/bartenders, a gift shop, clean changing rooms and bathrooms, and butterfly/hummingbird sanctuaries. There is a bobsled ride that also departs from the top of the mountain, which is an additional cost. We enjoyed the infinity pool and waterslide, which offer picturesque views of the ship as it is docked in Ocho Rios.