We have just returned to New Zealand after our third visit to Cabo. We hired a Jeep from Thrifty for 4 days. We were quoted a price of 90 USD a day and told by them before signing the CC slip that the maximum we would pay would be 360 USD. When we returned the car we were given a copy of our CC slip showing a charge of 4672.74 pesos. When queried why it wasn't in USD we were told it was company policy to change the amount to pesos and Thrifty's exchange rate was 13. Strangely Thrifty had managed to lose all the paper work we had signed when picking up the car.
My advice is use someone else, last time in Cabo we used National and had no problems.