Good for you guys! Mexico is very cool...
In Mazatlan and Puerto Vallarta, many of the cabs are little compacts, like toyota corollas. I have seen a van, or two, as well.
Also, in Mazatlan, there are open air cabs called pulmonias. These seat 4 and look like the old VW things. They sound like golf carts!
In both these ports you likely will dock at shore....not offshore like Cabo. So, the tender issue shouldn't be a problem.
When you grab a cab, remember to agree on a price BEFORE you get in. Often, cabbies will quote you the high rate. With a little practice, you should be able to get them down by 1/3rd, or so.
Enjoy your trip.