That is an extremely remote area. I have ventured west on state road 90 three times to Del Rio and I yet to have any luck at all. The country is full of hills and the road network is horrible at best, wit border patrol stops, and all I have had to show for it is an invitation to traffic court in Hondo for a busted headlight.
Though If you watch the radars on any day with half a chance of convection, you will see one or two cells start in mexico cross and into Terrel county with vils up to 80 and then die out as it approaches Pecos county. I have lost count the number of times I have watched that happen. On two occasions in June I saw two severe cells merge and head east, with reports of 3 inch hail or better and definite rotation, into Sanderson or even val verde county.
Its hit or miss and very very difficult to get to.