Summary - Saturday Rock is easy to get to, about two hours from Portland, has awesome views and a short, sometimes gnarly and steep, bushwhack. Park at 45.85645, -122.17190 and follow the ridge to the summit. The first clear area you encounter on the top isn't it, keep going! Trees to hang wires, easy 2M QSOs, good APRS connectivity, spotty cell service. National Forest parking pass required.
TL;DR - Saturday Rock has only been activated once, which is odd, as it is relatively easy to get to, the bushwhack isn't terrible, and there's plenty of room and trees on the top. ND7Y, Tyler, met me at the Sunset Falls Campground and off we went. Going up we took the 4211 route, which I do not recommend without 4WD, clearance, and a disregard for your vehicle's paint. Lots of holes, humps, and rocks to navigate on a very narrow, sometimes steep road. We came back on 42, which is longer but in better shape. It took about the same time either way. The Sunset Falls Campground gets crowded and requires a National Forest parking pass.
Once at the parking spot (45.85645, -122.17190) at the junction of 53 and 38, you will see the nose of the ridge that you will climb to the summit. Long pants and sleeves are a plus, as you will be working your way through patches of stiff brush and closely spaced trees. When you come to the first high flat spot, keep going. You will traverse a saddle and climb to the main summit (see the map). Overall, you will go up about 450 feet in a little over half a mile. A compass or GPS are handy as it is easy to get pushed east or west detouring around impassable brush.
On arrival, you will be treated to mountain wild flowers, and plenty of volcano views. You can see many of the other SOTA peaks in the area, too. You will have plenty of room to set up, all in the sun. The trees are relatively short but I was able to get a wire up about 20'. Both ND7Y and I put up masts. 2M contacts were easy, as was APRS spotting. Cell phone service was pretty spotty. ND7Y had better luck with Google than I did with ATT. There was no HF RFI to note other than a weird phenomena on 30 meters: a cyclic waves of static followed by a series of sharp bangs before the band noise dropped three or four S units. No idea what it was.
Two pro tips: Carry sunscreen and bug spray; the sun is bright and the flies are enormous. Take care on the Forest Roads. We encountered a couple of trucks going way too fast on roads that won't allow for two Jettas to pass one another, let alone a F150 and a 4Runner.
Overall, easy drive and not-too-taxing hike with great views and plenty of solitude for a SOTA activation!