Yes it's hilly, and it's high... it could get snow anytime, but compared to real mountains, I don't remember it being bad. And the route through the Columbia Gorge to Portland like it does is the easiest way across the Cascades, you follow the river so it's not steep or particularly winding ;~D.
At least there shouldn't be much traffic, I wouldn't think, except maybe near Salt Lake City and probably near Portland. So there's that...
I do need to decide if I'm gonna do it in two days or three. I'd rather three...but that does add to the overall costs. Still, it'd give me more leeway for bad weather and all, and I could arrive fairly early on the third day, most likely.
Colombia Gorge....mmmmmmmm......cherries....