Keep UMA in mind. Some Tmobile phones and most Tmobile Blackberries are UMA capable - which means they 'see' a wifi signal as a US cell tower when using a Tmobile sim. This capability is useful worldwide, even with prepaid Tmobile sims.

You won't want him to send or receive local calls on it unless he doesn't mind swapping for a local sim.

The classic Tmobile 8320 Curve is my international travel phone. Tons of them here.

Jim