"As far as the North Cascades, it appears that most normal visitors approach from the west side, so the Marblemount ranger station would make sense."
Yes. If you are coming in from the west you wouldn't be wasting your time to stop in for a chat. They a pretty knowledgable bunch, and passionate about the wilderness in a way that few other ranger station are, IME. They're just off Highway 20 in Marblemount.
"It appears that more animal studies happen east of the crest toward Mazama, kind of away from the people. I don't know."
This is true, although the majority of them seem to head even further east, especially to the area that includes the Selkirk Range. The whole northeastern corner of Washington has a reputation for being a good place for wildlife viewing. A lot of it has been logged over and is now in the process of regenerating, which means a lot of cover and food for the little critters, which in turn attract the big critters. You might want to check out Wikipedia's writeup on the Selkirks. It has a section on the fauna that will give you an idea of the possibilities, and also may put your mind at rest about the likelihood of running into a griz. In general, Eastern Washington doesn't get quite as much snow as the Cascades, which means you would have a better chance of getting 5 miles off road than further west in late May-early June, especially if you are hauling a heavy load. Mazama is just south of The Pasayten Wilderness and a couple thousand feet lower. I think you might have a hard time driving up to Harts Pass, the closest entry point to the Pasayten from Mazama, at that time of year. Remember, PCT hikers headed south starting around June 1, usually start on snow. If you do decide to try that area, it would be a good idea to call ahead to one of the local establishments to find out if the roads are clear, snow conditions higher up, etc. I've included one good place to call below. Good luck, Bob. If you get the right conditions, it's a beautiful area to spend some time with a camera, or without for that matter.
Mazama Store. 50 Lost River Road, Mazama, WA 98833. Phone: 509-996-2855.