Funny you should ask... I've been researching the same topic for my trip to Hong Kong. I just DON'T want to mess with the Chinese government.
This is a link to TSA's information, which will cover the domestic security. From what I can gather, bamboo would probably be best. Bring your best manners because the screeners have the ultimate say in the decision, but I think their focus is on bigger issues than knitting needles at this point.
Going through customs and security on the way back, I'll go ahead and run a tapestry needle (plastic, of course) and yarn through any work in progress so that if they won't let my needles through, I'm not losing my work.
Have a great trip!