Van Horn, TX to San Antonio by way of I-90 is 430 miles and should take about 6 hours of driving if you do the speed limit which is 80 mph in West Texas.
Van Horn to SA by US 90 is 460 miles and should take 7 hours of driving if you do the speed limit which I believe is 70 mph on the open road..... towns are small and widely spaced. You may hit a few stop lights and stop signs in the few towns you go thru that might increase the time a bit more.
Just thought of this...... if you are going to Port A (are you?) why would you want to go thru SA?
