Haven't heard of Ranger deployment yet.
The DPS has been called up.
Militia groups are filling some slots as well, and may yet fill more.
From the DPS website:
The Texas Rangers currently coordinate border security operations through six (6) Joint Operations and Intelligence Centers (JOICs) along the Texas-Mexico border and Coastal Bend area of the state.
I’m pretty sure a lot of other Texas resources are on the border including game wardens, drones, helicopters and a lot of DPS troopers like HG said.