I do not own a dirt bike but would love to learn to ride one and see if I like it before purchasing one. Does anyone know of any tracks in the OR or WA area where I could rent a bike and or receive some instruction? I rode minibikes as a kid at camp and enjoyed it.
I don't live anywhere near you, but I do have a dirtbike (have for more than half my life).
I'd buy an old Honda XR200. This bike is quite possibly the most bulletproof on the face of the planet. Have a friend who's mechanically inclined go with you to look at it and make sure there's nothing majorly wrong with it.
After you feel comfortable on it, then you can move on to virtually any dirtbike, based on your needs (motocross, trails, etc).