One other possibility is drive up Bridges Road past the complex. Keep going up and to your left. There is a house under construction with some parking available. Not sure what it looks like now with all this snow though. Might be buried.
Good luck and have a fun trip.
Thanks! FYI, about half of the cars at that turnout have green hangtags, which I suspect are for the neighboring complex (as you've mentioned). We didn't want to risk it. We did a pass through the neighborhood and construction was on-going at that house from morning to evening all weekend--must be on a time-crunch at that job!
Ended up parking at the Mammoth RV Park in their overflow lot, which is a giant, muddy mess. Don't park there unless you have AWD or 4x4, or you WILL get stuck. Walked a good 3 miles on Sunday morning to retrieve our car...and it appears I ran over a screw in that muddy mess while backing into a spot. Flat tire. And everything is closed on Sunday morning (Goodyear, NAPA, and even the auto stuff down in Bishop).
Happy end to this story is that I called up Jose @ JR Tire [(760) 937-0071 · 1422 Tavern Rd C-3. Mammoth Lakes, CA 93546], and even though he's closed on Sunday, came out to his shop early on a Sunday morning. He patched the tire up at a reasonable cost, and we were on our way. Still good people in this world.
Terrible luck all weekend, but oh well, at least we had a good day on Saturday on the hill.