If you want to rent a a car, RENT ONE.
You'll be perfectly fine. Just be aware of the rules (Mexico is a different country, after all), plan accordingly, and have fun.
We've rented cars in many different parts of Mexico. No problem. Ever. As long as you understand the local rules and requirements (just like anywhere else you'd travel to).
If you don't do something because "something could go wrong" or "a friend/co-worker/neighbor did ___ in ______ and had a bad experience" would mean that nobody would rent a car anywhere. Or buy a timeshare, ever. Especially in Mexico. Or go to a foreign country. Or cross the street in front of their own house, for that matter.
If you want to drive around when you're there, rent one (intelligently) with correct insurance, make sure you have travel medical insurance coverage too (like any foreign trip) and have a great trip. Easy peasy.