Columbia Area Transit (CAT) has amended their route dates/times. CAT will run to Stevenson on weekends during the summer for Dog Mountain runs, only.
You can take the bus across the Bridge of the Gods to Vancouver, Portland, Stevenson, Cascade Locks, Wyeth, Multnomah Falls, Hood River, The Dalles, White Salmon, Upper Valley, and other places throughout the Gorge.
And the Annual $40 GOrge Pass makes it even easier to get around, good for unlimited fixed route rides through December 31.