Taxi service isn't great in Xian, but no big deal. There's great bus service around town. If you want to get home a little faster, take a tuk-tuk.
There are so many around Xi'an that we got into a tuk-tuk traffic jam in this photo of the Muslim neighborhood. Be sure to negotiate the price first. Anything above 30RMB is a rip-off, unless you're planning to tuk-tuk your way home.