I'm in support of the car excursion idea as well if you decide in favor of getting off the ship.

The parts of town you'd be likely to visit (and the western side of the island in general) are pretty dreadful IMO -- ideal for those whose idea "fun in Mexico" is going to places with names like "Mr. Sancho's" and eating from buffets laden with poor interpretations of suburban Mexican food, but horrible for those with any interest in culture or good eating.

That said, the eastern side of the island is an incredible contrast to the other parts of the island and only ~20 to 30 minutes away -- there are no sights to see (and no electricity other than generators and windmills) --just a beautiful, uninhabited (protected) beach area with no one in sight. I understand that mom's not into the "beach scene," but if she appreciates scenery, it might be worth it do a loop drive.