Yeah, it's closed until October. Most of us who fish down there are pretty devoted to the river, and if we get wind of people fishing out of season, we don't hesitate to call OSP.
If you're floating it, try putting in at the Keno Recreation area, administered by Pacific Power. The turn-off is about 3/4 mile past Keno Elementary on the north side of the road. It is open dawn to dusk, so be careful parking there if you won't be getting back until late at night.
Roe Outfitters does float it. I saw them there twice in the last few weeks of the season. Darren Roe is a nice guy, and I'm sure he'd talk to you about where to put in.
Good luck this fall!