Not Americans, beware....
A tale for you to be aware of. A very nice American couple staying here had their valuables bag stolen at the airport whilst unloading their bikes. Everything of value was taken, including their passports, Despite very helpful consulate and Embassy services, they ended up in the "kafkaesque" situation where they had to fly to Madrid to get a replacement passport, but NONE of the Spanish airlines would allow them to fly without valid id, ie passport, despite the fact the policia Nacional at the Airport told them it was legal to do so. They got a flight with Airberlin who were very helpful, and got them to Madrid. So a coulpe of takeouts:
1) Dont leave doors unlocked in cars at the airport, thre is at least one gang working there
2) Try and keep another ID (driving license eg) separate
3) Fly Airberlin!