I looked at CSA's website and, as a Texas resident, was surprised to see this:

"Rental Car Damage (Not available in OR and TX)
Provides primary coverage if the car you rented while on your trip is damaged due to collision, fire, flood, theft, vandalism, windstorm or hail."

So Texans have to pay? Why?

Yeah, I was suprised to see that at the CSA website also...but cannot answer why TX is excluded.

Dariow, I would be curious to know what it is that is different between the VISA CDW coverage and the travel insurance?

I called VISA and also printed out the CDW program from their website. I know they won't cover lost hotel, etc...but all I'm concerned about is car damage and deductible which seems covered.

Some visa coverage is not out of the USA. Secondly, the credit card does not cover things like luggage or camera loss from an accident or cost of trip interuption.

Steer clear of Thrifty. We rented in Costa Rica for 10 days this month (March 2009). Nowhere in the emails did it tell us we had to purchase liability insurance for $19.95 per day. We purchased the extra Amex Premium Ins, but they say it's the law to have their special liability insurance, and they'd call a taxi to take us back to the airport if we refused it(we took their shuttle to Thrifty). No one in the long line was prepared for the extra $20/day either.
In Jaco, we found out that others, like Avis, charged $12/day.
Just FYI.

We are on vacation in Costa Rica right now. I booked a Thrifty rental through American Express travel, bought Amex premium rental car insurance, and checked with Amex to make sure that we would be fully covered and wouldn't have to pay for additional insurance when we rented the car.

At the desk, $20 extra per day or we couldn't have the car. I called Amex and the representative said my best recourse was to dispute the charge after the fact. When I asked to be transferred to Amex's travel office, I got an answering service lady who was generally annoyed by my calling on a Saturday. Not quite the seamless American Express experience I had hoped for.

The person who checked us in at Thrifty said that every single customer was surprised and upset by the additional mandatory insurance, but that I was the nicest one so far. And, believe me, I wasn't trying to be nice about it - at all.

There's no reason why Thrifty can't add this mandatory insurance into their "total charge" which includes taxes, except that they would rather deceive their customers than have their rates look higher than the competition's.