I am by no means an expert, but I will say this... So many folks travel to West Texas with the sole intention of bagging a Greyband. If that is the case, than more times than not you will leave disappointed. However, if you enjoy the area for what it is worth, you have a much better time. I like being in the desert. I like the scenery, and the vast array of reptiles that is available in the area. I enjoy getting out of the house and the peace and quiet.
The area your hunting in is probably one of the more or most difficult areas to collect an alterna. This could be one reason you are having a hard time. Like Joe Forks said, if you concentrate in one area you have a better chance of seeing something. This takes patience... I myself have a hard time sitting in one area for many nights in a row. So that is why you find me cruising a bunch. I find less, but I still have a good time. Remember if you drive slow, you see more but cover less ground. If you drive fast, you cover more road but see less of it. To drive fast you have to have really good lights and brakes...It is up to you to find what works best for you.
I wish you the best of luck. The first year is a tough one. I have mentioned this before but sometimes I think the road has a Rhythm to it. If you find that Rhythm, you can see lots of animals. Also keep this in mind, if it's hotter, sleep later, hunt later (until the sun comes up). If it's cooler start earlier and quit earlier. Myself I tend to get tired lately and find myself turning in at 2:00 am or so. That is a mistake on my part because I have seen an alterna at 3:30 am. Some have seen them at dawn.
So last but not least, I say find what works for you, and have a good time. Enjoy the area, and be careful.
Good luck,
Steven O