IANAL but my understanding is that non-competes are essentially unenforceable in Texas.
The general gist is that, yes, they are enforceable. The legislature keeps pushing for them, and the courts have, at various times, pushed back against them. There are limitations on them, but you'd have to talk to an attorney to figure out what they are -- I don't remember exactly what my attorney said. I do know that my attorney said my fairly typical non-compete probably would hold up in court.
While I signed this one, I've just flat out refused to sign them in the past. People seem to have the idea that the employment agreement is set in stone. For some companies it might be, but I've had some success pushing back against clauses I didn't like.