Also, when it's time to cross back over the mountains, I suggest veering north and taking highway 26 that goes right by Mount Hood. I've taken both it and highway 58 (which goes through the Willamette Valley), and 26 was a much more interesting drive. It also means you get to go through the high desert around Bend, which is an interesting contrast with the rest of the drive. (58 is shorter/faster, though)