For a lot of West Texas, the problem is much simplified. For much of that area there is effectively only one highway between the towns. So the route finding part of things is pretty simple. Instead you figure out the spacing of the towns and choices. To illustrate consider traveling the ~300 miles between Van Horn and Del Rio:
- At highest level there aren't many alternatives:
* US 90 all the way
* I-10 shoulder/frontage road and then cut across via 118 or 285 [Adventure cycling route does 118]
* I-10 shoulder/frontage road and then (some extra miles) to cut back across 17, 67 or 385
- Similarly there is a pretty small handful of towns; if you look for towns a pretty limited set of motels and somewhat more camping choices. Any warm shower choices are likely also to be pretty restricted.
- If you start off one from Van Horn - you have just a few choices if you want to end up in a town:
* Cycle to Marfa (~74 miles, with stores that might be open in Valentine or might not); one road, one route
* Follow I-10 to Kent (37 miles) and perhaps from there to Fort Davis (53 miles) or further to Balmorhea (32 miles)
So you essentially wake up and figure out (a) do I stay in Van Horn (b) do I go for Marfa (and perhaps Alpine after that) (c) do I go for Kent (and perhaps Fort Davis or Balmorhea after that). The routes are pretty easy to find, no GPS required. During the day,
adjust if necessary.

With that said, not sure I would categorize this as particularly boring or challenging - there is a lot of the US west like this, with wide open spaces and some distance between towns but with reasonable US highways between them. Worst comes to worst, since this is also primary route for auto traffic, you hitch a ride to the next town and sort things out from there, though unless you do something stupid, chances of running into problems are also low.

the interstate in that area has 'relatively' light traffic. wide shoulder of
smooth asphalt.

highway 90 even lighter traffic, but a fair amount of trucks. for much
of it you have a 3-5' shoulder, but it's a rough chip-seal.

the farm roads can be very narrow with no shoulder, and pickups wizzing
by at 75 mph.

will you be rushing through? any plans to ride big bend national park?

not sure about bus stations along the way, but there is an amtrak line.
unfortunately, many of those stations are no baggage car stops. carry
on baggage only.

I don't recall seeing any stores at all in Valentine. Unless something has changed since I was there or I missed something, there are no services at all in Valentine.

Did I miss something there?

It was a nice enough ride with VERY little traffic.

I've had a lot of positive results using a Garmin 800 for both preplanned routes and on-the-fly navigation, and in all three car/bike/pedestrian modes. The GPS gives me so many options to explore, or just get from A-to-B as quickly as possible, without the worry of ever getting lost ("lost" means not knowing where you are. with a GPS, that is impossible).

I have used this in N. America and many countries in Europe. Have a SD card loaded with 2 Garmin's City Navigator maps for N. America and Europe, plus for cycling I load OSM routable cycle maps on that same SD.

The 800 has been extremely useful in large cities providing turn by turn directions, etc. Not only do I use it while driving and cycling, but also on walking tours. This year we spent days walking all around Rome and Naples without a hitch. I tested my sense of direction in Rome and failed a couple times. Luckily we had the GPS to steer us back home.

While riding unknown roads, the GPS map acts as a "look ahead" so I can bomb descents quite quickly, knowing ahead of time when tight corners are coming up. When locals see you are at speed and competent, I have found they give more room and respect rather than treating you as a tourist getting in their way.

My #1 gripe is that the screen size is barely adequate for reading the map information. My eyesight is becoming more problematic in the last couple years and so I would really like a iPhone size display for my full-on bike/map GPS, but the new Garmin 1000 model is only marginally larger than the 800. The information available on the GPS is fine, it's just the map size/resolution that I'm finding problematic without reading glasses.

At some industrial safety stores they have wrap around safety glasses that work great for cycling that have reader inserts in the lower bi-focal area that help reading your GPS or computer.

I am not endorsing these, I only list this as an example of ones that the local (local to me) safety store sells. The ones I bought in the past are no longer on their website.
Jackson Safety Safari 3006 Readers Safety Glasses: Tortoise Frame, 2.0 Diopter Brown Lens

You just gave me an idea to search for stick-on bi-focal windows. My favorite cycling glasses are Oakley Racing Jacket, as these are the best to keep the wind and dirt out of my eyes. They have plenty of vertical space and so adding a bi-focal to the bottom of the pane would would well. I only need that for when navigating with the 800, so I can swap out those lens when not needed.

BTW, my race GPS is a Garmin 500 and never use that for navigating (in no-map mode). No reading glasses needed either

Paper maps. I like to get a sense of the days whole ride laid out, not just the next 2 turns. Does gps give you contour elevation and hill direction on the paved road? I usually try to figure out where I'm going to camp after the first day's ride and wing it from there. Aren't people riding out of cell/ gps range sometimes?

Sometimes directions from local residents are far better than a map. I remember I was once in VT at a diner in Ludlow having breakfast and had my map out planning my ride over Killington on Rt100. The cook told me that there was a gravel road just before the climb called River Road and that it would completely bypass the mountain. He was right and the trade of gravel riding rather than climbing was great.

I have used Optx brand stick on lenses with some of my regular glass sunglasses but have had less luck when using them on wrap arounds. The curve of the wrap around type lens did not seem to work as well.

Racing Jacket lens are sized more like regular and not wrap around, so the Optx may work. Plus, reviews on Amazon seem to indicate that the lower mag (1.0-2.0) are thinner and adapt to curved lenses better. I would only need a 1.25-1.5 to focus on the GPS @ handlebar distance.

Thanks for the tip.

Actually on my ride, I also didn't encounter anything open in Valentine. My journal notes from 2001: "Hills went away and land opened up as I got close to Valentine. Population 214. From the looks of it, at least four buildings in town were abandoned cafes and three were abandoned gas stations. Nothing open currently or place to get water. Wonder if all four were open at the same time, or just serially tried different buildings." However, I somehow also remember reading other journals about people being able to fill water (other than my journal note above, I didn't try very hard).