In response to an enquiry from a poster on the Africa board here are some suggestions for dining in Xi'an:
Xi'an is most famous for it's noodles, dumplings and street food. There is a fantastic night market (also open in the daytime, but most exciting at night) in the vicinity of the Grand Mosque, where most of the street foods can be easily had. In all the trips I have had to Xi'an I have always eaten at this market and never had any health issues. In particular try the liang pi (cold rice noodles mixed with vegetables and a sesame-based sauce), rou jia mo (round breads filled with succulent beef or lamb), biang biang mian (excellent wide wheat noodles with a spicy beef sauce), yang rou pao mo (lamb soup into which you break Xi'an's flat bread to make sort of dumplings). Be sure also to try the dried fruits and nuts and the various nut candies, which demonstrate that Xi'an still remembers the traders who came via the silk road, bringing Middle Eastern treats with them.
Among restaurants, De Fa Chang, on the main road just to the east of the entry to the night market, is "the" place to go for Xi'an's rather touristy "dumpling feast", an entire meal consisting of nothing but dumplings (you choose how many courses you'll get, and the level of fanciness of the fillings, and it can be surprisingly expensive). It's OK if you're into dumplings, but honestly it does get to be too much and the restaurant is so touristy that it has become a mecca for thieves (my camera got stolen while there last October; the cops said it happens all the time).
At the terracotta soldiers there are a few restaurants that serve quite good local cuisine, though the menus are only in Chinese and no one speaks anything but Chinese (and many speak only local dialect at that). But they have been very friendly and since they're so surprised to see foreigners they really bend over backwards to make you happy. There are also vendors on the parking lot grounds who sell the meat sandwich things and the rice noodles and other typical street foods.