the problem is he is leaving tomorrow.
I just got an education in buying unlocked phones. a lot of places sell them, such as Best Buy, J&R, Staples, Target, but none have them in stock. all ship only.
Buy any phone from t-mobile or AT&T (full price) and ask them to unlock it. T-mobile used to give you one free unlock per year. So I don't know if it still costs anything to do it.
the best solution for tourists in the US who want to buy unlock phones to use out side of US is to buy them from small specialty shops who only carry such products and he found one and bought a S3 and a S4.
T-Mobile said they would unlock 45 days after purchase.
There are many websites providing unlocked Samsung phones online. Just make sure it is unlocked before purchasing because sometimes they send phones which are not unlocked.