My partner and I were very lucky to meet Mr Lee. We didn't get to spend as much time with him as we would have liked, but will certainly see him again next time we are in Xi'an. He is friendly and knowledgeable. It is clear that he loves his town and knows its secrets.
He was also very accommodating when we just wanted a simple lunch and were rushed for time. I know there are a lot of English speaking guides, but I definitely recommend Mr Lee if you get the chance. We were able to contact him via email and he responded quickly. He said it was okay to give out his email, so here it is: firstname.lastname@example.org
If you read this thread and also get to meet Mr Lee, please share your story here.