It all depends, if you are tendering or docking. Tendering costs a lot of time, so maybe you have less time in Key West. We also have done the Conch train tour. There you can see most parts of Key west. After the tour you can stroll through the streets, take a look at some boutiques and make a stop in the bars.
But my opinion is, that they are only interesting in the evening, when they have live music and its more crowded. But unfortunately the ship leaves at 2 pm.
You can also make a tour with an electric car and visit all the places you are interested in by yourself.
Enjoy Key West, we loved it. And of course the rest of the cruise.