I imported the P25 DPS Trunked system this morning....Working great!
Maybe I am too far away for the conventional P25 system?
In many cases. DPS uses the VHF channels in "duplex" mode, not through a repeater.
The base transmits on one frequency (the ones labeled DPS Base A, B, C, or D).
If you're reasonably close to the dispatch office, you may hear that, since it's usually a good signal.
But, the mobile units are answering on a different frequency, from an antenna mounted on the vehicle. Generally, unless you are within a few miles (maybe 6 to 8, the exact distance is going to vary depending on terrain, are you on a hill? are they? what kind of antenna are you using? etc), you'll never hear them.
For areas where the "dispatch" frequency is one of the repeaters (usually 159.2100 or 159.2175), like this one:
159.21750 154.67250
KVX672 RM 123 NAC DPS RPT 08
Columbus - Dispatch
You'll hear both sides of the conversation on these (if you can hear the repeater).
I can't speak directly to how much use there is in the Houston area on the Vhf channels. Here in the DFW area, though I can hear Dallas DPS base without a problem (they're about 20 miles away on the other side of the county), I almost never hear the mobiles, unless the dispatcher switches the console to "repeater mode", which sometimes occurs during a chase. Even the base traffic is much reduced, as units use their MDT's for routine traffic markouts and subject checks. West of the metro area here, towards Weatherford & farther west, I do get a lot of radio traffic from Mineral Wells DPS dispatch.