I live in Texas...familiar with the area. In college I worked for the Texas Ag experiment Station and we had cotton fields west of Weslaco. Depending on the place along the river, there is high ground. In places where there isn't high ground...I would consider clearing it or building a tower. I guess an AK might be a good brush gun if you have no other choice. But my point is this more general I guess than confined to THIS particular location: If given OTHER options...I would take them. Not every rancher along that border has flat brushy land to defend...and in places where possible...I'm sniping.
Make sense?