Plano... Richardson... Irving... Frisco... Lewisville... Denton... The Colony... Arlington... are all substantially bigger than any SA suburbs, and then you have about 10 more that I didn't list that are roughly the size of a place like New Braunfels.
Over Christmas break when I was last in SA my mom and I went just north of 1604 towards Bulverde and it was a crappy two-lane two-way road like you see in the country. Basically a cow path
Not to say there is NOTHING outside of SA, but other than the 35 corridor it's really sparse... SA really has next to nothing to the west, due east and especially south.