I live in central WA state and have ridden at least hundreds, perhaps thousands of miles on I-90 near my home.
But the I-90 bridge over the Columbia at Vantage is an example of what many people are talking about - a death trap. No shoulders, heavy traffic, high speeds and high winds at times. Still waiting for the old railroad bridge at Beverly to be opened for cyclists - but will probably die first. Wouldn't it be nice to have a ferry from the old highway landings? Old Vantage Highway on the east side is stunning. I've hitch-hiked across major rivers about a half-dozen times. Have thought about doing so there.
It's tough to find a good place to cross the Columbia in central Washington - obviously Wenatchee is a good choice - and thus, I will often plan my route using the limiting points - river crossings & mountain passes. Another possible crossing of the Columbia is at the Hanford Site east of Yakima - narrow but not that much traffic.