The problem is that most prairie dog towns are located on pasture/range land that for the most part is private property. Thye only way I know of is to find and area that has some PDs and start asking around for permission to shoot them.
They are everywhere up here. Just drive around public land to find them. I would wait until after the antelope season though. Lots of "outfitters " selling prairie dog hunts . Seems odd to pay for them but some do.