Cruzer, from downtown I'd go up to Washington Park (if you can find the back way up on a path from SW Jefferson near the MAX tunnel you win a prize), find Fairview near the Rose Garden, go up to Skyline, hang a right for a little ways to Barnes Rd., then left to destination. the last 1/2 mile on Barnes is likely not too fun (higher traffic & minimal shoulder), but there's really no alternative to getting there that i can see.
Note the use of "up" in the above.
the
www.ByCycle.org route mapper offers a route (not what i'd recommend, very indirect & extra climbing), as well as the ability to check out the Metro bike map (hit the "show map" button)