Yeah, there are lots of good areas to hunt in the grasslands. Look up the park department website in Medora, and order a grasslands map. It's not real expensive but it shows most of the roads, and private/park/grasslands boundaries. Lot of private land intermingled in the grasslands, and you sure don't want to get in the park with a gun. They get rather grumpy about that. If you get into Beach or Wibaux hang at the local tavern and visit with a few of the local ranchers/farmers and tell them what you're looking for. Everyone else is beating their door down looking for a place to deer hunt, they'll love you wanting to shoot yotes! And, probably put you on some real good territory.
If you've never hunted the badlands, it can be a strange place to hunt at times. It'll look like flat and level prairie; you'll see critters, and then suddenly, they just disappear. Lots of washes coming off the hills across that flat land. We watched 4 mulies disappear one day, and we swore up and down that it was flat level prairie. Started walking out toward where we last saw them and found a wash there that had cottonwoods 35 - 40 feet high growing in it, and we couldn't see a leaf from across the flat and level prairie.
If you don't have reservations, drag a camper, or carry a tent, or something... Rooms are hard to come by out there during deer season. And, with the oil field goodies going on out there, I'm going to guess it will be just about impossible all overthat end of the state. Haven't been out there in several years, but most of the guys that planned on going out there during opening week of deer season, made reservations a year in advance. Helps if you know someone, which we did at the time, and he got us a room. You can try the motels in Medora, don't know if they're open for hunting season, there used to be one there that did stay open.
Shamrock in Wibaux used to put on some fantastic grub! If you left there hungry, you weren't human!! Might want to check into that. Opening weekend there'll be a feed in Beach on Friday night at the VFW.
Beautiful country, it'll spoil you! Be sure to take a good camera along, you'll want lots of pictures. North unit is much prettier than the South unit if you do any site seeing, deeper cuts, bigger hills. Whole lot rougher country up there.