Xi'an: Seeing the Terracotta Warriors
It's better you have a local guide/friend and go to the place by bus. (Taxi takes too much when 2 hours way from Xi'an to your destination is needed)
China: Street photography in China
1. Sure,it's accepted to take photos of ordinary people and it's not rude at all 2. Not sure about that. If possible please do not take photos in front of government buildings.