Sounds like a great trip. I actually went to Sturgis during the rally last year after spending a few days in Idaho to ride through Oregon and Washington. While we headed to Stugis, we rode through Lolo Pass (Hwy 12)...probably one of the best roads I have ever been on. While we were staying in Stugis, we visited Devils Tower, Badlands, Spearfish, Deadwood, Black Hills, Mount Rushmore, Custer Park...on the way home, we also visited Yellowstone, Grand Tetons, Bryce National Park, and Zion National Park. The trip was approximatly 5,000 miles in 15 days. It was an awesome trip...one I would love to do again.

I don't recommend going all the way into Devil's Tower...not much to see...and to me, not worth the entry fee unless you already posses an annual National Park Access Pass. There is a photo op area that most people just pull over to, to take a picture of your bike with the tower in the background.

As for yellowstone and custer park, there are buffalo there. For the most part, they are used to bikes and visitors, but I actually literally came face to face with a buffalo at yellowstone. So close the buffalo couldnt really figure me out while I was on my bike. He decided to approach me head on, and looked straight at me and my bike. I just kept staring at his big horns. Buffalo licked my headlight and continued to cross the rode. Later that day, there was a report that a heard of buffalo ran into several Harley riders. In short, just be careful around wildlife and enjoy the gorgeous senery.