Erik,
Nice website with some excellent photography you've got there!
Broad-banded Copperheads are very abundant in the sandy Post Oak Belt in southern Bexar and northern Atascosa counties, although they are not the easiest snakes to find by road cruising.
I have lived near Pleasanton for the last twenty years and cannot remember ever seeing one on roads around here, although I sure they occasionally do cross. However, last May I found seven in my backyard without even looking for them (haven't seen one since, and only a handful before then).
On some property I own between Seguin and Stockdale, they are easily the most commonly seen snakes (even more than garter snakes). I have found them in every month of the year except for January but, unlike many snakes around here, they don't seem to surface much during the winter, even on the warmer days. They tend to reappear by the end of February in normal years however.
Tom Lott