In the past, I had heard good things about Mexigo Tours but according to recent news articles, many are having problems. According to this article from the Respuesta newspaper , American tourists are reporting they paid for a tour and the company never provided the service. The article states more than a dozen complaints have been received about this company. Also , they report the company had no insurance and used tour guides and vehicles without licenses.
Just a heads up , to use caution.
Here is the Respuesta article in Spanish: