There's a small mistake in that route. Don't ride down W. 11th Ave in Eugene; it's a mess. It's so bad that a local chain of very bad bike shops is actually paying to put some signs up on it to direct cyclists to a nearby path, the parallel Fern Ridge Bike Path. Just east of Terry, some people continue on the bike path to Greenhill and then come back south to Crow Rd, but it is faster/safer/better to take Ed Cone Blvd to W. 11th/Hwy126 and jog 100 feet east to cross over to Crow Rd. at Diess Feed. Mike, the owner, is cool with cyclists cutting through his business (just wave and say hello if you see anyone). After hours he has some barricades up that you can easily get around.

Oh, by the way, if you are on the bike path during darkness, be wary of nutria. They like to forage on the non-creek side of the path, but as soon as you start to go by them they hasten to the water. They are large enough to take you down if you hit them wrong, so don't.

I suppose you have all the state campground info, but just in case, the one on Lighthouse Rd in Umpqua Lighthouse State Park is rather convenient to the end of the Smith River.