Your straightest shot is I35, but that takes you thru Dallas/FW and Austin, both harder to drive thru than San Antonio. The shorter and more scenic would be Wichita Falls, and taking 281 to San Antonio. My choice would be avoid Dallas and Austin. If you are not pressed for time, 281 splits south of Wichita Falls and you can pick up 16 and take it to the Texas Hill Country. Easily spend a night in Fredericksburg, Kerrville. From Kerrville, change to 173 to Bandera. Then 173 south to Jourdanton. That picks up 16 again to Zapata on the Rio Grande. Or ease East somewhere to pick up 281 or 77 depending on where in RGV you want to go. Depends on whether you want to just make time (I35) or see the sights. Either way, happy trails.
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