You can go to Carnival's website (
www.carnival.com) and click on "Shore Excursions" then "Mexican Riviera" then each port destination to see what's available.
Puerto Vallarta is a charming town of cobblestoned streets and lots of shopping and oceanfront restaurants and bars. If you want to get outside of town, I recommend going south to Chico's Paradise and/or Chino's Paradise. These are places where rivers come down off the mountains and form waterfalls and pools to swim in (each has a restaurant overlooking). Of course, each looks very different depending on the time of year and how much rain they've had. To get there you can rent a Jeep or even hire a taxi driver--but make a "deal" with him for the entire trip (don't let him drop you off there because it's hard to get a cab back!!). I checked out the Carnival website and couldn't find an excursion that explicitly mentions these places but they may be included in their "jungle tours."
If you're just hanging around in Puerto Vallarta and want a GREAT experience, have a cab take to you to Chez Helena, then climb the stairs up, up, up to their "El Nido" Bar. It's on the rooftop overlooking all of Puerto Vallarta and is fantastic. Last time I was there I could even see whales in the distance.
Mazatlan--I've never really found anything much to do there. You can either go out to El Cid (which is a nice hotel) and lay on their beach and have lunch, or go to Senor Frog's and watch (or participate!) in getting crazy. There is, however, a really beautiful expansive beach there.
Los Cabos--the stop there is really brief and they "tender" you in (the ship doesn't dock so you have to go to shore by boat). If you take an excursion there, I'd recommend one of the cruises; or else just do some shopping at the pier or in town.
-Randy
P.S. The Pride is a great ship in my opinion.
