If you're visiting Portland, Oregon and you're looking for a great way to go visit Multnomah Falls or Rooster Rock, then plan your trip via the luxury bus line service which departs Gateway Transit Center and is a collaborative metro area project in cooperation with TriMet.
Check their website for daily scheduled trips. It's economical, and exceptionally convenient. Ride out to Multnomah Falls on am early departing route, stay all day and hike, then return on an evening departure returning back to Gateway Transit Center.
LINK:
http://columbiagorgeexpress.com/