Mutt, be advised that 3G or more specifically UMTS in Europe and the rest of the world operates in the 2100 MHz band. In the Americas it is on 850 MHz and 1900 MHz. There are not many 3G phones or datacards that operate on both 2100 MHz and 850/1900 so even if your friend gets a US pre-pay SIM card he probably won't have 3G access.
What about WiFi access? There are access points everywhere in the US....many of them free. Your friend could still use GSM roaming for voice calls.
IO540 voice is also carried on 3G, along with SMS, MMS, WAP, video calls, data etc.
Hope this helps,
KDY
Last edited by KiloDeltaYankee; 24th May 2008 at 16:36.
Reason: clarity