btw, here goes the offical weblink which might help u for planning ur future drive tour in Mexico...
http://aplicaciones4.sct.gob.mx/sibuac_internet/ControllerUI;jsessionid=1JsGNYbGL29VBybpD8pC8lDGjHRDQNTjDJC05yBJj5ltgnZJy9k1!-1392584287!-2124763955?action=cmdEscogeRuta&eligeIdioma=si
i'll be visiting several ancient ruins & towns in central-south area next week.