There's no telling without your own observation. Where I usually hunt near my home, the only water sources are sparse cattle tanks, the climate is quite dry, and I've yet to see a single deer drink from them- then again, I pay little mind to the tanks and perhaps I miss them on the rare occasion that they do. They favor the greener vegetation in the draws between hills, and that is where I focus my attention. Spotting them is the hard part, as brush can provide significant cover, but the good thing about mule deer country is the hills can be a huge advantage to sneaking up on them once spotted.
Bottom line: observation is key. You may note that water sources are fairly active, whether by seeing the deer or noting tracks. Or your deer may be like the ones I hunt and they stick to the draws and cover.