Marc, the Cingular solution would be the easiest for you. You just need to switch your card to a new quad band phone for use overseas. If you don't want to buy a phone, you just need to borrow someone's phone and put your card into the phone (if they let you).
For Europe, you need a tri band phone. If a triband works, I have an extra one and I can lend it to you when we travel together.
