Can I use a Passport Card to travel to Cabo or do I need the traditional Passport Book?
From the State Department: “The new wallet-sized US Passport Card is a travel document that can be used to enter the United States from Canada, Mexico, the Caribbean, and Bermuda at land border crossings or sea ports-of-entry. Note that it cannot be used for international air travel.” Therefore, if there were an emergency and you needed to leave the ship from Cabo and return to the States, you could not do so with a Passport Card.