Well, I was just in the San Francisco visa office last week, and I can tell you you can only go to the Visa office closest to your house. We live in Austin TX and were told that we can only go to the Houston office.

The rules are changing very fast, so be careful. Note you will also need documentation of where you are staying and proof of your plane tickets. If you are traveling with children, you will need their birth certificates to prove their relationship to you.

This page does seem up to date, and contains a map of the areas:

http://www.china-embassy.org/eng/hzqz/zgqz/t84246.htm