Also, there are some risks involved in renting any motorized vehicle in Mexico. Your regular car insurance does not cover you at all. More critical is the fact that they do not maintain things the way we do here. The cruise ships arrange tours with the ones they know have decent standards. But, doing it on your own, you risk having a breakdown or even an accident. I know of several people who have had bad experiences. So, just be aware of the risks. And, I agree with Trip that there really isn't much of a need to do this in those 2 ports.