This hike is part of our top favorites and will not disappoint, and you do not need a pass to enjoy it! The roads are great getting there, though there was heavy traffic in the Hoquiam/Aberdeen area because of construction. The views you get of Lake Quinault as you travel up South Shore Road are excellent precursors to the hike, too. Everything was well marked and we found the trailhead with no problems. You'll see a seemingly overgrown dirt road to the right of the main one at the sign for the canyon; it may seem a bit sketchy, but my mustang could handle it and it will take you directly to the actual trailhead, where the information board is located.
The page describes it as a "deep, dark canyon," but this doesn't mean what you'd normally expect; the canyon is so vast and wide that you don't really realize it is one until you're done with the hike. Not far from the trailhead, you'll come across a large log extending out and up in front of you, and it looks like it is part of the trail - it's not! We walked up this log (see pictures) and then two others before we reconnected to the main path and didn't even realize we had wandered astray until we were back on track. We're not sure how much time we saved or what we missed by this shortcut, but don't be alarmed if you assume that it is part of the trail.
The further you hike, the rockier it will get, and there are a few notable places where there are logs you have to go under or where it is extremely overgrown (the latter of which is mostly toward the very end of the trail). Don't let these things deter you from making it to the end! We hiked exactly 2.5 miles to reach the beautiful lunch spot - fallen logs, glistening rocks, and beautiful waterfalls await you! There is a large log right as you emerge from the forest, from which you can see the waterfall and other logs up ahead. We climbed up the side of it (it looks like steps were cut out) but on our way back discovered that it was much easier to start at the very end of the log.
Being the adventurers we are, we chose to explore and get as close as we could to the waterfall (be careful with this, as some places are sketchy and the rocks are VERY slippery near the falls). We ate lunch right next to the falls, with our feet hanging over the edge over the clear blue pool, and continued exploring higher up after that. Round trip, we went about 5.4 miles (2.5 both ways plus adventuring) and had a blast the entire time. We highly recommend it and are dying to go again!