Looks like I touched a nerve. Not surprised with Amex or State Farm for that matter. I have Progressive and Master Card and was double covered. Best advice with any insurance as I previously stated, contact your insurance carrier and credit card company explain clearly what you plan to do and be guided by them. If your covered, you'll save a ton from the cost of coverage through the rental car company.
ps Lori, don't take yourself so seriously!!!
1) I have driven in Mexico many times, especially in the area you are going to be in. If you have driven in any big American city you have all the abilities you will need. If you have just a bit of sense you'll have no problems. Watch out for the speed bumps (topes) they can be anywhere and some are huge, nothing like driving along at 50mph and suddenly hitting one! This is the main reason you see all the warnings of not driving at night, it's harder to see these things.
2) Purchase the full coverage in Mexico, rent with your preferred CC, but don't rely on any of that coverage. Even with full coverage Mexican insurance and the best CC coverage, keep in mind if you get in an accident and hurt a Mexican you will go to jail and be kept there until you can see the judge. Do it on Friday, you won't see the judge until Monday and will spend the weekend in jail. You will be required to financially compensate the Mexican you hit in cash by order of the judge for injury, medical and lost wages, and you won't be released until you can do it, there are no insurance coverages Mexican or your CC that will pay this or keep you out of jail. The only way to avoid any of that would be paying the person you hit in cash, on the spot, but if the police show up, you're going to jail. Search the internet there are plenty of stories of this, people missing cruise ships, etc...
3) Rates quoted for a rental car have a cheap daily rate, but that's without insurance, you need to add the insurance and that will at a minimum double the daily rate, use that as your budget, not the daily rate.
4) Rent a car or not? Who the hell knows? Do what you want and can afford. Only you know how much driving you will do. If you're only there for 3 days are you planning on driving all around, up and down the coast? Do you not care and just want the freedom to drive yourself back and forth from the airport each way? You have to figure this out, this is such a short stay there is no financially right or wrong answer, only your convenience is at stake.