I DON'T CARE IF YOUR CREDIT CARD OR HOME INSURANCE COVERS YOU OR NOT, ALWAYS GET FULL COVERAGE INSURANCE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
TRUST ME, THIS IS THE VOICE OF EXPERIENCE SPEAKING!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
If you don't want to spend AT LEAST one full day of your valuable vacation time dealing with the police, car rental and insurance people, (should something happen), GET THE FULL COVERAGE INSURANCE!!!!!!!!!!!!!!!!!!
The minimum price of getting the full coverage insurance, which I think a lot of the rental places make manditory nowdays anyway, is far less than the hassles you will encounter without it.
Your homeowners or Auto insurance in the US WILL NOT cover you while in MX. There are specific exclusions for MX.