The GSM 3G iPad is not locked to a carrier, just pick up a Pay-as-you-go (prepaid) microSIM in the country you're visiting and away you go.. (I'm UK based, normally with Orange in the UK, but currently posting this using an Omani Omantel 3G microsim).
Buy a CDMA one and you may as well try and use a brick to connect to the internet with via 3G internationally. Actually, the brick might be more successful.