If you can find the TH, you are half way to the mountain. Fortunately, the people of Mexico are extremely friendly and everywhere we went there are always people willing to help with direction. Hiked with Matthew.
My first time visiting Monterrey, and I was very impressed with the ruggedness of the peaks surrounding the city. Pico Perico is an enjoyable hike (remember to bring a flashlight for the mine that you must hike through!), and the class 4 scramble up the gully is great fun. Summit views are often hazy because of the smog around the city, though.