I know in the past people on this board have been told that they are not allowed, but Stephenson Preserve for example is full of caches. This person can probably give you the official answer:
--- In CentralTexasGeocachers@yahoogroups.com, "dn_shults" <donald.shults@...> wrote:
> This is maybe a touchy question...
> A cache in my area recently popped up in the Blunn Creek Preserve. I was under the impression this was not allowed?
> I only ask because I've had a prettay killer hide I've dreamed of for ythat area for a long time! lol
> On a side note, I think its important we respect the city's rules about caching in order to keep a good reputation and a farily loose policy.
> Sorry, I just think its important to know.