I travel that route all the time commuting between El Paso and my job near Hobbs. The road is fine. Mostly 2 lane but there are passing lanes in the areas where they are needed.
As it was said by another, this is a 130 mile stretch with no fuel service so be sure that you have enough as you leave El Paso. Another thing to be aware of is the lack of cell phone coverage in some areas.
Where are you planing to stay while visiting the caverns? No personal experience with any of the area parks but the general concensus on the forum is that the KOA to the North of Carlsbad is the best. A few miles out of the way but worth it.
You will have the relatively short but steep grade coming up to Guadalupe Mountains NP but just take your time and all will be fine. You should also consider stopping at the Guadalupe visitor center for a few minutes on your way through. It is the highest mountain in TX and a really interesting place.
Feel free to PM me or ask here if you have any specific questions. I will do my best to help out.
Terry
