Salsa club (or Shasha as it is called by Chinese) is very nice place to visit when you want to have fun: to dance, to drink or play. It is easy to meet new acquaintance there as everybody feels themselves relaxed and open even for foreigners.
Salsa is located in the very centre of Xi'an to the west from the Bell Tower. The best time to come is about 9 or 10 p.m. - there are a lot of fresh, cheerful, but yet not drunk people willing to have fun. As it said before, the booze is rather expensive, especially in comparison with average prices outside, but it is only your decision to drink or not to drink or where to drink. The entrance is free of charge. So, theoretically the whole evening can cost you 0.
The music is always modern and nice. Waiters are rather friendly and can find place for you even when all the table are occupied. By the way, different tables cost different. For example, one big table for 6 persons costs 400RMB. This money you give in the capacity of prepayment for drinks and snacks. The club works to the last client (watch here: http://www.youtube.com/watch?v=dl_OTRowTpA).
All in all, the place is remarkable and very nice.