Don't overpay for a car rental in Mexico.  This can easily happen to you in Cancun and Playa del Carmen.  There are numerous Hertz and Avis stands in prominent locations.  Often, however, these appear to be lightly supervised--if at all--by the franchisor.  You can easily be overcharged and directed to a non Hertz or Avis location.  For example, a quote of $75 for a days rental can easily include $20 for the person who "rents" to you and $5 -10 for the person who drives you to the car location.  If possible, it is best to locate an actual local agency off the busy tourist strips where you can easily find a car for $39-49 a day.  And, don't accept any car that looks to be in less than optimum condition.  Your hotel or tourist police info booth should be able to direct you.