He got caught on a cactus called a nopal. The people of Mexico like to eat nopales. They scrape the thorns off, dice up the cactus and eat it like a vegetable. In the background on the left you can see an outhouse with a blanket for the door. The homes and churches in this area do not have indoor plumbing.
Stanley went across the bridge that spans the Rio Grande. About halfway over he got his picture taken on the boundary line between two great nations: the USA and Mexico.