El Paso and Houston are about 674 miles apart by road. Split the difference and you arrive near San Antonio, the city closest to the halfway point between them. That puts roughly 10 hr 31 min of driving on the El Paso side and 3 hr 58 min on the Houston side — the fairest single meeting point among the cities near the middle.
That's a half-day drive from each side, so San Antonio suits an overnight or a weekend rather than a quick coffee — long enough to want a reason to stay, short enough to drive.
If San Antonio doesn't have what you're after, Austin and Dallas are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between El Paso and Houston.
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.