From Portland you'll drive south until you can get on Highway 214 around Woodburn. Another 30 minutes or so and you'll hit Silverton, shortly after that you'll lose cell reception but start seeing signs for the Silver Falls State Park. Head through to the end - there are lots of stops and trailheads along the road, but you need to pay for your pass, first.
The South Falls at Silver Falls State Park is one of ten waterfalls in the park, the easiest to get to, and is one that you can walk beneath - so you can imagine that it's hard to get a clear shot without crowds of people in frame. Thankfully, in the afternoon most people that are still around the park have already made their way through this section of trail and so a there weren't many people to pose for this shot. The spot is easy enough to reach at the bottom of the falls, over a small bridge and out to some slippery rocks. I can't wait to get back to this spot when there is some snow (and of course, get out to the other nine waterfalls again as well).