Mex, Puerto Vallarta is not only hot but humid. I would probably want either shade or A/C under these circumstances.
Depends on your habits, too. Staying all day inside the trailer at 90 isn't smart. It's more comfortable in a hammock under palapa or near water. Huge mass of water and adjacent layer of air kept at constant 75 with some breeze, nice. Two hundred feet inshore it's an oven. Take a shower - yes, goosebumps instantly. Beautiful.
Up to 85 is fine in my books, and I am from BC. People who get overheated at 75 to the point that they need a fan or A/C - you gotta be kidding. But, if so, - they are not suited well for these adventures, and I don't think that Northern roots are the main reason. Probably have dietary issues and other restrictions too. Comfortable temperature zone shrinks when you get old - not old-er, but old, that's the sad truth. Remember South Park episode where Stan threatens the residents of Seniors Home to lower the thermostat down from 76 to 75.5? :)