I am in Corpus and travel to San Antonio and Austin often. I hear DPS at home and on the road all the way with no problems. That said, you will hear much more traffic if you lock in the system. With all the other traffic and DPS being "short and sweet" you usually are hearing something else when DPS is transmitting. I also hear DPS car-car via the San Pat node on the Costal Network.
I am in Houston, I think I hear them more on the TX WARN p25 system channels which are simulcast with 155.465 for instance.
But much less than in years past, unless something is going on (pursuit, special ops etc.) Occasionally on Harris County or other SO channels also.
Regarding encryption, that is negative for TXDPS as far as I know, unless you are talking about CLE or TX Rangers, etc.
Houston PD TAC chs are now encrypted, that may be what the previous post refers to.