The US State Department just put out another warning about travel in Xinjiang. When in doubt, don't be dumb:
The State Department alerts U.S. citizens to safety and security concerns in the city of Urumqi in China's Xinjiang Uyghur Autonomous Region. This Travel Alert expires on August 10, 2009.
On July 5, 2009, ethnic violence erupted in Urumqi. The unrest continued in the following days, with Chinese state media reporting over one hundred and fifty deaths and more than one thousand injured. There is a significant increased security presence in Urumqi and its environs; sporadic outbreaks of violence may still occur.
There are no indications that this violence is directed at U.S. citizens; however, Americans in Urumqi and throughout Xinjiang are advised to avoid areas where demonstrations and large gatherings are taking place. U.S. citizens in Urumqi should remain indoors and avoid unnecessary movement within the city. Americans planning a trip to Xinjiang are advised to defer travel to the region at this time.