Plaskett Creek appears to be between the two current Hwy 1 closures, both longterm, one for bridge being out and one for mudslide. Caltrans road conditions page shows some one-way spots, but it is not clear to me if you can currently reach Plaskett Creek without going over Nacimiento-Ferguson road through Fort Hunter-Liggett. That road may not be open to TT's as long as yours appears to be. You might try calling the USFS Monterey Ranger District (831) 385-5434 or the camp concessionaire (805) 434-1996.
101 to Hwy 46 over the hills to the coast should get you to San Simeon Washburn camp without any problems.