In Mazatlan the El Cid resort in the Golden Zone allows cruise passengers to use their beach and pool at no charge. There is a small fee for towels and change rooms. Food and beverages are reasonably priced.
In Puerto Vallarta, The Hideway at Las Caletas excursion was $89 and The Beach Break excursion was $59. I'm sorry, I don't remember the name of the resort for the Beach Break--I think it was a Marriott or a Sheraton . . . friends that went there said it was fantastic.