I have heard elk bugle before opening weekend. There are a lot of things that can change how the season runs. The biggest being weather. But the time frame you are talking about is good. I have not seen the muzzle loaders have a great impact on my hunting, but I out walk most of them. And that has always been a big key. Your biggest key will be getting in shape to handle the altitude change. They are long days, starting at 4 and ending long after dark[7:30ish]. It is beautiful country and a great time of year to be in the mountains.
Gselkhunter