Pop through Yellowstone and head for Missoula. From there head down 12 and make Lolo Pass along the Clearwater River. 70 miles of twisties until you get sick of them! Head to Yakima from there and come into St. Helens from the Windy Ridge side. Lots of fun forest and a lot less traffic. You cannot get to Johnson Observatory from there though. 2nd on Crater Lake and Newberry Volcano. Spectacular, but, it's hotter than hell in central Oregon this time of year because it's nothing but a giant pile of lava. Eastern Washington will get hot also but nothing like Bakeoven Road.
And yea, that's a real road!