My wife and I made our first-ever trip to a GPAA claim on Labor Day 2018. The claim directions are spot-on. We parked on the narrow shoulder adjacent to the highway, but it is fairly busy with Yosemite traffic. Heavy or wide vehicles not recommended. There is a paved shoulder just south of the claim within easy walking distance, though. I called and spoke to the USFS station prior to going and was told we would not need a permit to prospect.
We had more gear with us, but the steep access was too difficult to navigate with anything other than pans in our backpacks. This claim is not accessible if you have any substantial physical limitations or concerns. Use caution regardless.
The river would have been perfect for a sluice box, but we could only try a number of test pans. All we got was black sand from points in, near, and above the waterline. We could have crossed the river to the other side in places but did not.
Overall, this is a nice spot to spend time. We hope to go back again sometime and try our luck again, maybe at the claims nearby.