These are the US Embassy in China websites, where you can find up to date information, travel tips and safety issues. Before coming to China it is a good idea to inform a US Embassy in China of your destination and duration of stay.
This is the main US Embassy in Beijing website link, http://beijing.usembassy.gov/
Guangzhou US Consulate website link, http://www.usembassy-china.org.cn/guangzhou/iv/
Chengdu US Consulate website link, http://www.usembassy-china.org.cn/chengdu/cons/
Here is an all around good website for the American Embassies in China, http://www.usembassy-china.org.cn/