No worse than the rest of southwest Texas. The good news is unless you reach for one or step on one, they let you know they are about to bite you before they do.
In my younger days I kept a very large rattler in an aquarium. It taught me something that I have never forgotten, and think about often while in the woods.When I would get close to the glass, either intentionally or accidently, it would do one of two things: either sit there rattling up a storm, or strike. It NEVER rattled if it was going to strike, and if it was rattling, you had to get after the glass to provoke a response. Maybe it was just that particular snake, but it really makes you wonder.