GPs wrote:
We are not sure best routes between those two cities especially considering so many issues along the southern U.S. border.
Those 'issues' are mainly media hype and political posturing. There are some concerns near the major population centers in the lower RGV, but those seldom impact RV folks. You will drive through some CBP checkpoints, and see many CBP vehicles.
We spent May, June, July as campground hosts at the Chisos Basin CG at Big Bend NP. I certainly would not recommend trying to take anything larger than 30' into the mountains, and there are only a couple sites that would hold such a rig for dry camping.
Big Bend is definitely worth a side trip. The RV campground at Rio Grande Village is nothing special - just a parking lot with FHU - but the park is worth your time.
Concur with others - take US-90, not I-10 at least as far as Del Rio.