I just started paying really close attention again this year/part of last year - mostly because of PRO. It seems like the rugby hub(s) has moved to Austin with Dallas holding pretty steady. I'm pretty sure that Houston doesn't have a D1 team at this time. Austin and Dallas each have 2 (again, I think).
But, there is a TON of grass roots rugby going on in each if these cities. The Woodlands won the HS state championship this year and 2 of the Austin schools were ranked in the Goff Top 10 most of the season. Katy, my old club, was Top 25 most of the season. There are at least 4 big Youth clubs (U11 and younger) in Houston, alone.
ThisIsTexasRugby shared a list of clubs in Texas and there are SO MANY! The game has really grown since I started playing in 06 and it's really exciting to see.
I'll try to find a link:
http://www.texasrugbyunion.com/2017/06/07/2017-rrrc-promotion-and-relegation/