Wirelessly posted (The Roaming Phone: Mozilla/5.0 (iPhone; U; CPU iPhone OS 2_1 like Mac OS X; en-us) AppleWebKit/525.18.1 (KHTML, like Gecko) Version/3.1.1 Mobile/5F136 Safari/525.20)

Wow, I just went to the website and looked at the T&C, and there's no misreading it: they will take a 10% deposit of the vehicle's value. (Good on ya for reading the T&C--too many folks don't!)

Sometimes actual policies are not quite as stringent as what the website lays out, though, so I'd still recommend calling to confirm. I'd try the number listed as the shuttle dispatch number, as that will likely get you straight to someone at the rental counter, who will be the one renting you your car and will know definitively what will be held on your card--that number appears to be 624-145-7800, ext. 716 (I think the 624 is the MX country code, but I'm not sure). If that doesn't get to the rental staff, ask for the number or to be transferred (it might go to the hotel front desk if the hotel operates the shuttle).

If that really is the policy, a call to customer care and/or the president's office is definitely warranted. I know Mexican driving conditions are notoriously bad and most insurance policies do not normally cover Mexico, but a $3,000 hold is excessive for a $200 rental.