I had a similar itinerary in May/June except that I picked the car up upon arrival in Madrid from Barcelona at the Atocha Railway Station. We then drove through Andalusia for nine days before finally spending a few days in Madrid and flying home from Barajas.

What I especially liked about picking the car up at Atocha was the ease of driving out of Madrid without having to deal with central city traffic.

I got a great rate through Costco, €330 including all taxes and fees, for nine days for an Audi A4. At pickup, I was upgraded to a virtually new - 1,900 km on the odometer - Audi A6 Ultra Turbo Diesel with navigation. Using my United MileagePlus Explorer Visa card, I was fully insured and did not have to purchase any additional protection.

The only trick was booking the car for pickup/drop off at the railroad station. Costco Travel enabled me to reserve it only for the airport. After a few tries, I made a reservation for the airport and then pulled the confirmation up on Avis' website and changed it to the railroad station.

Have a great trip.