renting a car at Madrid airport. CDW get it or wave it?

Credit cards will cover CDW. Your credit card company should have a phamplet indicating if there is a limit. I also get Cdw through Allianz for $9 a day. CDW through the rental car company is expensive. Be aware that neither Allianz nor your credit card will cover liability or personal injury. If you only have CDW and hit a car or person, you would be on the hook for damages, so consider getting those from the rental car company. With Avis, personal injury is about $13 a day while liability is $3 a day. Remember, you will need an International driving permit.

Edit: Having just been to Spain, liability is mandatory so it comes with the price of the rental.

With the exception of the extra insurance provided by AE, I would not rely on a cc insurance. There have been several reports and one personal experience with cc companies looking for a loophole to bail out of providing the coverage. It is third party coverage and it is easy to look the other way while you are trying to deal with the rental agency. I would not do it. Remember you have a contract with the rental agency and the CC insurance does not. CC insurance is only responsible to you.

thank you for your advice. I don't mind paying for coverage as long as there is coverage.
I would like to be free of worry. I normally take trains, taxes and buses but I will be travel to more remote locations on this trip.

This website has a page on Car-Rental Insurance and the Collision Damage Waiver (CDW).

I would recommend checking out gamut.com for more detailed information on your question. They have a great pamphlet on "Renting a Car Guide in Europe" on this website. It will answer your questions about personal injury and property damage, etc. I used my visa card for the insurance on CDW. Andy helped us for a 3 week trip covering Germany, Austria, Hungary, Slovakia & Czech Republic last year and a two week trip to Portugal this past April-May.

Call Visa and they will email a letter stating your coverage that you can give to the car rental company in the language you want. I rented a car in Madrid and took the letter from Visa in Spanish in case the agent asked. There are some important details you will find in the pamphlet from gamut.com that you can follow. For example, don't use one cc card to rent the car and add a second drive at the pickup point and use another cc card. You want to use the same card to cover all of the charges on one cc card. Visa will also send you their contract and what is covered. Do your research and then make an informed decision. Hope this helps.