You're right to be concerned about grizzly's in those areas, because there are plenty of them in there. Keep a clean camp, keep your head on a swivel, and carry bear spray and you should be alright. If I had to leave an elk and come back for it I'd try and suspend it high between two trees, well away from the gut pile. A griz might still be in the area but at least he couldn't "claim" the elk.
I have hunted NW Wyoming multiple times, but have yet to see a grizzly bear. I know they are around, however, and the advice above is spot on. Use basic precautions and be alert.
