Is The Carnival Paradise all non smoking now? It was not when I went in March 2010. I wish all ships were totally non smoking but that is another topic.
I am booked with my 2 teenage daughters on The Splendor in late March, as my kids have never done a MR cruise. I have read many reviews of things to do on cruisecritic for Cabo, PV, and Mazatalan and not as many sounded as negative as the article Paul wrote. It sounds like many cruise passengers just go to beaches or places within 1/4 mile from the cruise dock and that is their impression of the place. The area around the ports in most countries is not usually representative of the whole city, you have to go a bit farther to have a better experience. I think if you do a little research before you go you can find some fun things to do in the MR that are not scary.
I went to Progreso on a Western Caribbean cruise this Nov and many people said it was dirty, had many locals bugging you to buy their trinkets and the cruisers did not like it. I found the people very sweet and friendly, yes they were selling things, but that is how they make a living. I like being a traveler not a tourist where I go which means keep an open mind. I will let you know we liked the MR when we get back from our trip.