I have never fished the John Day river in Oregon, but it is reportedly an awesome small mouth fishery. You can spend a week floating the river, it's remote, you'll see very few other fishermen, and there some great scenery. There are guided multi-day trips or you could do your own. Of course, doing it yourself would mean bringing rafts or pontoons, all the camping gear etc., but it would be one heck of an adventure. If you went in mid-September, you should get nice weather - warm days, cool nights, perfect for camping. There's also other Oregon rivers that have great smallie fishing.
If you're in Washington state, the Yakima river below Ellensburg is well populated with wild rainbows, it's catch and release, single barbless hook, it's best in late September/October, during the summer it is high and murky due to irrigation run-off. Two lane highway parallels the river through Yakima canyon which allows plentiful bank access. Being accessible, it gets lots of pressure, you would want to fish it during the week. Alpine lakes in the central Cascade mountains can be awesome, especially the ones that require more than 6-8 hours to hike in. Really helps to bring a tube or raft so you can get off the bank. Most of the lakes hold cutthroat, some rainbows, and there are a few with brookies. You won't get any over 2 lbs., but there's lots of them. August and September is the time to go, the snow is out and the weather is dry.