Thank you for your information on Seattle. That is extremely useful! You are right in that we were looking to decide as not sure how much time we are actually going to have on our trip (Portland meaning a longer trip).
If you are able to provide any information on Portland that would be extremely useful. Thansk so much, I really appreciate it!
Well, to Portland I'd do either route I suggested to Lewiston ID for your first overnight. From Lewiston I'd take US12 past Walla Walla to where US730 cuts to the left toward I82 at Umatilla. Take I82 the short distance south to pick up I84 on in to Portland.
From Lewiston you can also cross the bridge over to Clarkston WA on US 12, then follow State Road 129 to Asotin WA, then up the grade to Anatone WA. From there continue to Enterprise Oregon (going down Rattlesnake Grade to the state line where the road changes numbers but there is no choice of route so just keep on). From Enterprise head toward Lostine and on to LaGrande OR to get on I84 west bound. This will be a much slower route to I84 as there is some mountain driving thru the Blue Mountains.
The shortest route is to leave Yellowstone by the West entrance at West Yellowstone, drive US20 to Idaho Falls. Get on I15 to the I86 cut off to I84, then I84 west to Portland. This takes you across the not-so-scenic -to-me high desert of Southern Idaho. Lots of huge cattle feeder lots and dairy operations in the Twin Falls/Jerome area.
We did Portland to Salt Lake City last month, with three nights in West Yellowstone. I found St. Regis to be the ideal spot between West Yellowstone and Cle Elum (east of Seattle). It's a very small town with only a Super 8 as far as hotels, but the hotel and visitor center there were all exactly what we needed. A local yurt Air B&B owner responded to one of my St. Regis posts online, and I saw they offer it for a really great price ($60-$75 or somewhere around there), so things like that are worth considering, too.
Of course that assumes you take I90 toward Seattle first. We'd never been to Oregon, Washington, Idaho, Montana, or Utah (had visited southern Wyoming from Colorado in 2014), so our route was designed to see as much of those states as possible along I90.
Happy to help with any other particulars anytime if you do that route. Good luck and happy travels either way!
P.S. Multnomah Falls in the greater Portland area is an absolute must. One of the most gorgeous waterfalls I've ever seen, and super close to the road/parking.
for a stopping point it depends on your route and final destination.
If its seattle you would go 90. The best stop is Coeur D'Alene and roughly the mid point. this is farth3er if you go to potylandf because you would go 395 to tri cities then cut down to 84