When you ask the locals where to go if you only have a weekend and want to ride the best trails they will likely tell you to do the Alpine Trail. The Last two thirds of the trail into town are a big descent and it is frequently done as with a shuttle. It can be climbed by riding up logging roads, however in the middle of the summer this can be a long hot boring climb without much scenery. If you do ride up road 1910 do it early and bring plenty of water, an mp3 player or some company. The ride down is awesome. Generally earning your turns is higher moral ground for mountain bikers but this is one case where the climb is long enough that unless you are in racing shape you might enjoy it more if you do a shuttle. That is if you are doing the whole thing as a loop.
If it is a hot day there is are some excellent swimming holes upstream from the covered bridge. The easiest one to find and one that is frequented by the locals is about three and a half miles up the North Fork Road (paved) (N Fork Rd @43.794115, -122.452720) This is a world class swimming hole. Nothing in the
One other thing to mention is that at the start of the trail if you are ridding up there is a large black berry patch near the covered bridge parking area. You ride right through the middle of it and there are thorny branches crossing the trail for about a hundred yards. Walk or ride? You decide.