Contact Mina . . . 594-956-0313 teotipark@prodigy.net.mx . . . who owns the place and talk with her. She knows the area better than anyone. She speaks English very well. She knows the roads and the rules.
Mina can also tell you how to get in and out of Mexico City. You can leave your rig there while you go into the big city. You can go by bus and subway from Teotihuacan or Mina may be able to hook you up with a guide who will take you into the city. Stay in the city at a hotel for a few days while your rig rests at Mina's.
The trick to getting to Teotihuacan is the route you take. Teotihuacan is not in the Hoy No Circula but some areas you pass through could be. The safe way is taking the Arco Norte to 132D. It can depend on where you are coming from.