hey.. i just did this in september east to west (see here http://trackmytour.com/tZzSC). i took 84 (from boise) to hermiston and stayed entirely on the washington side (tho crossing over for overnights) until I-205 near portland. september may be a bit late in the year but it was fine on the washington side w/ not too much traffic. there is a section right out of hermiston that's 83 miles between services (tho towards the end there is a convenience store that may be open). the washington side is certainly more scenic but quite a bit hillier (if you're not used to climbing you may look longingly at 84's nice flat grade). i've certainly ridden on significantly worse roads than highway 14 -- i didn't think anything of it, actually. nice ride.