Sandy and Dee,
With regard to your Mexican Riviera ports:
>> Cabo San Lucas is a great "playground in the sun" with phenomenal beaches, snorkeling, diving, and boating. A couple years ago, I took a shore excursion that combined a ride in a glass bottom boat to "land's end" with a couple hours at a beach resort. The boat ride offered the best of both worlds, combining a good view of the coast and its wildlife with a good view of the fish Both aspects of the excursion were thoroughly enjoyable, so I probably would do it again if I return.
>> In Mazatlan, there's a shore excursion that combines a folkloric show with a tour of the city highlights that's definitely worthwhile.
>> In Puerto Vallarta, the shore excursion that visits the city highlights is again very worthwhile. If I remember correctly, you'll see the tower divers (similar to the cliff divers in Acapulco, but they dive from a tower rather than from a cliff) as well as some magnificent art in the Church of Our Lady of Guadalupe and in the town hall.
Have a great cruise!