Both Potatoe Patch and Mingus Campground sites were full by Friday at around 5PM in early October. We were told by the camp host we could go down Forest Service Rd 132 for dispersed camping. Before the road gets too steep, there are flat-ish sites off the dirt road. Even those were mostly taken, so we were able to double up with another camper at a site that was pretty large (and a pull through!).
It was incredibly beautiful, quiet and shaded with nice trees, though these primitive sites were very rocky and rutted.
I took a star off for not expanding sites at the other campgrounds. I do recommend, but get there early!