Completed the loop as described in the Backpacking Washington guidebook. I elected to do the hike as a 3 night trip to maximize time at the lakes and tarns. This is a real adventure!
According to the USFS website, there is still a road washout on Forest Road 26. However, you can drive to the Green River Horse Camp trailhead from FR 26 coming from the south. There is a Road Closed sign just north of the turnoff to 2612 from 26 as there is still a washout on the north end, so it is not accessible from that side until the road is repaired. But the red warning sign on the Goat Mountain page on the WTA website ("6/1/17: trail inaccessible; road washout") is NOT accurate - you just have to take the route from FR 99 to 26 north, past Ryan Lake, to get there.
The descriptions in the book are mostly accurate and camping spots are in the places they are reported. However GPS or equivalent smartphone app is highly recommended as at least one trailheads is challenging to find and there are multiple places where the trail has been rerouted from the Topo map.
Vanson Lake and Deadman's lake are both gorgeous, accessible, very tranquil and quiet in September.
One major concern: there is a trail washout very early into the hike from the Green River Horse Camp west on 213 just as it crosses over into private land. It is possible that there is a reroute further back the trail; I didn't backtrack to see but it certainly wasn't evident or marked. As of this writing, the washout is 10-15 deep gully about 20 feet across. It is not passable. I was able to track north about 300 feet by doing so hiked around the gully but this required pushing through deep brush and over a number of downed trees in wet, slippery conditions. It's really hazardous and I've written USFS to see if it can be addressed. There are other places where brief off-trail rerouting is necessary but none are what I would consider a hazard.
Expect patches of snow this time of year on the 217 side especially if heading up to Vanson Peak. Daytime highs were in the upper 50s and night temperatures dropped to freezing on Goat Mountain.
Good berry picking on 217, which is much better kept than 213. My mileage for the loop was 25 miles, including the short hike up to Vanson Peak and back. There is AT&T cell service on Vanson Peak but none elsewhere on the trail.