Your question is a little more complex than you think. If you will go to googlemaps.com and drill down to the Pecos River Bridge, just a little to the east of Langtry on Hwy 90. You will see, in the satellite view:
A nice parking area at the east end of the bridge on the north side that will let you view the river from the east abutment of the bridge. You can easily turn your rig around there.
If you travel a little more to the east you will find a turn off on the south side that will lead you to a high rest area that overlooks the bridge and the river.
If you go a little futher east you will reach Seminole Canyon State Park that has a walk down into the canyon where you can see pictographs.
