Mike
Contributor
If the rental car company forces you to purchase insurance it's a scam in itself. From my understanding every rental car in Mexico comes with the legal amount of liability insurance. If you are comfortable with this amount, quite often credit cards cover the collision/theft/etc. Just print any information regarding existing car rental insurance from travelers insurance policy or credit card and bring it for proof - read the fine print on the rental agreement. Stick to international companies (which are more affordable through hotwire.com) and don't let anyone twist your arm into purchasing an unneeded additional policy. They will try to frighten you, but if you know the rules, eventually they will soften and giggle when they realize you are too clever to be caught by their scam. Book your car before you arrive and bring the confirmation. Check all features for function before leaving the parking lot.
You should really look into the details of this. It's not as simple, cut and dry as it seems you might believe. You have very limited coverage from your CC company and even less from a US based insurance company. Make sure you contact both before assuming you have any coverage whatsoever, but even if you find you have some, I guarantee you don't have it all - there are a whole litinay of issues, such as lost income to cover to the rental car if it's wrecked, covering damages in cash before you are allowed to leave and of course the big one of covering lost wages if you injure a Mexican.