I guess it depends on how long you're planning to stay, but I've heard good things about Champoeg (pronounced 'shampooey') State Park, just south of the Portland. It's quite pretty, with several miles of bike & hiking trails. They have both full hookup and electric only sites. You can reserve spots online with ReserveAmerica.com, or call the campground at (503)678-1251.
Good luck, and maybe we'll see you around when you get to town!
Sean & Sharon
AIR #: 27389
TAC #: OR-3