James,
There used to be a Texas state director for American Atheists, but she needed to resign. From what I understand, AA is looking for a replacement. Some of the ACA members have considered signing up for it, but I don't believe anyone has stepped up to the challenge.
The ACA is affiliated with American Atheists, but we are not directly part of that organization. The ACA's focus is primarily Austin, but we do follow Texas state issues, as well.
The ACA has hosted a Texas-wide conference of atheist and agnostic groups for state-wide coordination a couple of years ago. We would like to do it again. As with most volunteer organizations, it's a matter of finding committed volunteers to take on the challenge. (There's enough interest state-wide that such a volunteer would have lots of help.)
--Don