This large sign is at the start of one of the two main scenic loop drives - Ajo Mountain Drive - in Organ Pipe Cactus National Monument. (The other bigger loop - Puerto Blanco Drive - probably has a similar sign but I didn't go there). The monument straddles the USA-Mexico border and includes a border crossing (at Lukeville, about seven miles south of this photo). At the northern entrance to the monument, about a hundred feet before the sign welcoming you to national monument, is a border patrol checkpoint. On the two plus hour drive out from Tucson there were not many vehicles, but I would say there were at least as many (if not more) border patrol vehicles compared to private vehicles.
