The fair place to meet is El Paso, TX — the city closest to the midpoint of San Antonio and Tucson. From the farther side that’s about 10 hr 31 min of driving.
Recommended midpoint
El Paso, TX
From San Antonio
10 hr 31 min
502 mi to El Paso
From Tucson
5 hr 33 min
265 mi to El Paso
Tucson has the shorter trip; the split is off by about 4 hr 58 min. The alternatives below can even it out. San Antonio and Tucson are about 765 miles apart.
San Antonio and Tucson are about 765 miles apart by road. Split the difference and you arrive near El Paso, the city closest to the halfway point between them. That puts roughly 10 hr 31 min of driving on the San Antonio side and 5 hr 33 min on the Tucson side — the fairest single meeting point among the cities near the middle.
That's a half-day drive from each side, so El Paso suits an overnight or a weekend rather than a quick coffee — long enough to want a reason to stay, short enough to drive.
If El Paso doesn't have what you're after, Albuquerque and Austin are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between San Antonio and Tucson.
El Paso is a city in and the county seat of El Paso County, Texas, United States. It is the 22nd-most populous city in the U.S., sixth-most populous city in Texas, and the most populous city in West Texas with a population of 678,815 at the 2020 census. Read more →
San Antonio is a city in the U.S. state of Texas. It is the seventh-most populous city in the United States, the second-most populous city in Texas, and the second-most populous city in the Southern U.S., with a population of 1.43 million at the 2020 census. Read more →
Tucson is the county seat of and the most populated city in Pima County, Arizona, United States. Read more →
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.
Estimates use straight-line distance and typical road speeds; real drive times vary with route and traffic.