When I brought 836KT home from Kansas State my first stop was at Rawlins, WY (RWL). The next morning we went west and overflew Kemmerer (EMM) and over the pass where US30 crosses the mountains, then north west for a fuel stop at Burley, ID. That leg required a bit of zig-zagging to cross the mountains NE of Salt Lake, but we were able to fly the entire route at 10500'. From Burley we overflew Boise then stopped at Pendalton, OR (PDT) for fuel and lunch. Then home from there. Crossing the Cascades in Washington at any of the passes can be done at 8500' if the wind isn't too bad. Higher if you want to minimize the head winds. It's rare that the wind isn't westerly over the mountains here.
If you're headed to Portland there is a MOA due west of Pendalton that you'd want to skirt, but after that it's an easy shot down the Columbia River canyon. Just don't fly too low through the river valley. Between The Dalles and Portland there are several places with power lines that stretch across the narrowest parts of the canyon and are more than 1000' agl. But you could easily fly that leg at 4500' if you wanted too.
