Yes, it's true that modern cars, properly maintained, don't cause much trouble, even in extreme weather. In summer, many car manufacturers test vehicles in Death Valley. You may see them zooming along the roads, putting the cars through various cruel and unusual maneuvers. They have permits from the Park Service to do things that you and I would be cited for doing.
You will see signs just before some long, steep upgrades suggesting turning off the a/c to prevent overheating. These days, this is just a suggestion--but DO IT in the event your car does overheat.
I will be on summer break after the first week of June, and it's time to start thinking about my vacation travels. Maybe I'll see some fellow TAs in Death Valley! Look for the "Silver Mule" tooling around the Valley :)