GoMadrid,

I haven't used this service yet, but have come across them several places recently. I just got a SideKickII at the beginning of the year which is a world phone but I had to wait 3 months before they would unlock the sim card so I could pop it out and use other sim cards.

This service looks like you can get a sim card delieved to you in the U.S. BEFORE you leave.

Telestial

If you do use them, let me know how it goes. I am impatiently waiting for my next trip!