Ur son is already having a degree from an international university. Now he can really excel his career if he joins a university in US and wil explore campus diversity. Life is easy for him (atleast 10 times easier than Poland) regardless of the state he selects. Please don't select the state or city, just focus on Universities. He needs to clear TOEFL, that is a requirement. Moreover some universities would prefer him to have GMAT examination. If there are any questions, u can contact me at ruchittt@rediffmail.com.
