The Texas borderland is an entirely contradictory place. In some areas thriving communities exist. In other places nothing is seen except green border patrol trucks prowling the hills. They make their presence known by the wisps of dust they leave behind. Life on the border has never been easy but things were better in times past. The population has been declining in some areas of the border for decades.
If you look carefully there are interesting relics of the past to be photographed along the Texas-Mexico border. But there are things to consider before jumping in with both feet. In the old days rattlesnakes and scorpions were dangers. Today, desperate people, some armed, may be present. There has always been a certain freedom of action practiced along the border. Today it is more overt and sometimes deadly.
A general rule in the Western United States is commerce follows the railroad. Interesting ghost towns will be within a few miles of rail or improved road transportation. Today highway 90 is the main road in the area. It follows the railroad right of way for the most part. To start exploring you need some good maps, a vehicle with high clearance and a desire to explore. The history is there you just have to go find it.