People from Xi'an can normally understand standard Mandarin, as it is the language that is officially taught in Chinese schools, but they generally speak the Guanzhong dialect. It sounds a little more slanted, for lack of a better word, than the Sichuanese dialect in Chengdu. It sounds softer, and I believe it would be the Chinese equivalent of what the Midwestern accent sounds like in the U.S.
All of China uses the Renminbi (Yuan).
A bottle of water normally costs around ¥3-4, which is about USD$0.50-0.65. That's cheaper than it would cost in the U.S.
The best meal I had in Xi'an was roujiamo, dubbed the "Chinese burger." It is essentially a thin bun, similar to naan bread in consistency but not in thickness, filled with shredded sauced pork. It is often served with just the pork or one can choose to add green vegetables.
