I've ridden from Lake Oswego to and/or from Albany a few times, roughly following that route. Once I combined the Canby, Wheatland, and Buena Vista ferries all into the same ride. Make sure the ferry is running and not shut down due to high water this time of year. Camping at Willamette Mission SP might also be a problem if there is high water. Take maps. You'll see some signs for the route, but unless it's a lot better that it used to be you don't want to depend on the signs to tell you where to go.
The area south of Salem is a bit hilly as I recall, depending on what route you follow. If you're in good shape, start early, and assume your in for an all day ride, it seems reasonably within reach.