I don't know about Montana, but the bulls in eastern washington, well atleast in my area, aren't really screaming yet. I've been hunting hard for the past week and I have heard two bulls.. The weather has been so hot..
I am using an outfitter seeing that I dont own a horse. I am going on a rifle hunt for Elk and Muleys. They pack you 20 miles into the Bob. It should be fun. Thats good to hear there bugling.
I was out last weekend and it was still pretty quiet. I called a bull in for my brother-in-law second day of the season and we now have meat in the freezer, but he came in quiet. You can still hunt effectively even when they aren't very vocal- it's just a lot more fun when they are screaming.
You should have fun in the Bob. I have heard there are some monster bulls in there. The weather has cooled this week, so hopefully it will be enough to get them going.