I'll be going into the Ansel Adams Wilderness next week for Ritter/Banner. I just discovered Agnew Meadows Campground is still closed. I'll be getting up to Mammoth around 9p on Friday and hitting the trail early Sat. Any chance I can still camp here without hassle?
Might just hunker down by the hot springs off 395.

You could just park at the trail head and sleep in the car or nearby. Also, if you go up to Minaret Vista, there's a big dirt lot to the left of the paved road, I've parked in there overnight a couple of times and slept outside of the car with no hassles. You just need to get in thru the toll booth prior to 7.