This is an old railroad bed that is a double-track trail. Small rocks, sand, a few climbs. Pretty easy ride along the river. Old box cars up toward the old, Harrison Ranch. You can camp up there if you like. I've seen mountain sheep, deer and other minor critters up there. Bring a flat-tire kit or/and extra tube... lots of goatheads.
From Portland, take I-84 east. Go past Hood River toward Celilo Village. Take exit for Deschutes River Recreation Area. Turn left at end of ramp; follow signs (about 2 miles) to entrance. Trailhead is up the bank at back of parking area.
http://www.singletracks.com/item.php?c=1&i=8746