The route is regarded as safe as far as gang activity is concerned. Hwy 120 through the Sierra Gorda is quite curvy with occasional fog, and local traffic can be unpredictable, but no more dangerous than driving highways in urban areas of Texas. Spectacular scenery. There are some falls you can walk to near Pinal De Amoles.
Huasca Secreta near El Naranjo is a non-budgety hotel/Lodge right on Salto El Meco, and which I believe offers the only access to such. With a car you can easily visit the falls of nearby Minas Viejas. Tamaño por is right on the highway, and while there are no hotels on site, there's a handful of decent taquerias. There are a number of hotels just minutes from the falls, and Puente De Dios is close. Sadly, when we were in the area last we didn't make it to Tamul.