This is a question almost every (Western) visitor to China asks with trepidation. But really, you have nothing to worry about. Chinese people love food, they love feeding foreigners their food, and Chinese food almost universally kicks a massive amount of ass. Huzzah.
A few quick tips:
- Chinese people don't really understand dietary preferences. I was discussing the Hui Zhu (non-Uyghur ethnic Muslims) with an extremely intelligent friend who said, "Yeah, they don't eat meat. I think they think pigs are gods." Ummmyeah. So if you keep strictly kosher or halal or are allergic to anything, you may have some issues, depending on what the food item is. But that by no means precludes your enjoying Chinese food. Just make sure you learn how to say what you can't eat, and watch out. "Bu yao ____" means "Don't want___," but if you're deathly allergic it's probably better to say "Wo bu hui chi..." which means "I can't eat...," OR "Ruguo wo chi ___, wo si." That means, "If I eat ___, I'll die." No messing with you.
- Oh, and MSG: Again, I'm a bad person to talk to about this because I never had any problems with MSG. But there's probably MSG in most restaurant dishes. You can ask for dishes without, especially when getting street food. The phrase here is "Bu yao wei jin."
- **IMPORTANT**: Don't drink the tap water. You can brush your teeth and of course wash with tap water, but no one in China drinks straight tap water. You're supposed to boil it first. And almost everyone drinks hot water, even without tea.
