Go big or go home :) You guys have a huge state!
Dallas, houston, san antonio, austin, corpus christi are all relatively in the same "region".
The guys out west in el paso, lubbock, midland, amarillo usually head west for most of their trips.
Arkansas, Oklahoma, and louisana would also fit well into the region as well
Just for reference, its about 650 miles from dallas to el paso, and about 420 miles from dallas to corpus.