AS I understand, google does not block you from using GV from overseas as long as you setup GV service by using an US ip address. However, I think China does blcok google a lot. I persoanlly using GV on my VPS which is located in UK with a French IP and it works perfectly. I also know some cities in China block regular sip ports which I had to either use a non-regular port or to use a stun server.