That's a pretty broad area with a lot of geographic and cultural diversity. Since I live in Seattle and would like to stay in the region after retiring I have thought about a lot of options but they all have their pluses and minuses.
Bellingham region is pretty cool and a college town. Downside being that it has grown a lot and is more crowded with all that entails. Vibrant cycling community.
Eastern slopes of the Cascades in Washington namely Methow Valley and Leavenworth area. Both get inundated with tourists especially in summer. Methow is cheaper but more remote especially in winter when the highway is closed. Lots of biking especially on forest service roads.
Puget Sound islands. Lots of choices from very hard to get to (private boat) or ferry serviced ones. I have friends who have lived on several of them and they all have their selling points. More remote ones like in the San Juans are harder to get on and off because of limited ferry capacity but also are quieter most of the year. Vashon, Bainbridge and Whidbey all have nice road riding and reasonable things to do with good access to the major metro areas.
Port Townsend is a cool town, some decent road riding and access to the Olympic mountains.
Most of the coastal town in Washington seem pretty isolated and touristy in a bad way. Lots of rain and limited roads means traffic if you are riding on the road.
In Oregon I'd certainly put Sisters/Bend at the top of the list but so have many other, hence they are growing and prices reflect that. Lots of riding both paved and unpaved plus other outdoor activities.
I like the Ashland area, nice warm weather, lots of roads, small college, Shakespeare festival but you are isolated from major metro areas and prices are pretty high for housing.
Norcal across the border from Ashland in a town like Mt. Shasta has a ton of riding, maybe the best as far as road riding that I've seen in the region but your aren't near any big colleges or major metro areas.
I don't know a ton about Idaho but Sand Point is a nice area with lots of forest service land and a great ski hill nearby. Prices don't seem insane compared to the rest of the region. McCall is nice for winter sports and I assume gravel riding, traffic on the paved roads seems pretty heavy the times we've been there and the proximity to Boise seems to have pushed housing costs up a bit.
The region's population as a whole is growing at a fast rate, places that were out "in the country" when I was growing are now essentially suburbs for the metro area. I'm not a huge fan of riding bikes on busy roads and unfortunately it seems like it gets busier every year in the entire region. I don't currently own a gravel bike but assume that if I'm going to ride regularly post retirement that It will be a requirement.