Easy answer: NO!
A)Spend a little time with travel books from your library, or on line, to find information about your ports.
B)Then match what there is to do with things you like to do.
If there are beaches, and you like to spend time on a beach, the decision should not be difficult.
Similarly, if you are near Mayan ruins and you are interested in history and culture, think about checking them out. Can you get to them by taxi - or is a group tour better?
If all you want to do is drink and buy trashy souvenirs, check out Senor Frog's and hang out with the souvenir hustlers.
Part of enjoying a cruise is planning for the cruise -- do some thinking and planning.