Favorite Place in CA
Where do I start.... The Rock Creek area of Bishop has tons of little campgrounds off the road on your way up to Rock Creek. Each one of them is unique and beautiful. The campsites down lower such as French Camp and Iris are a little hotter and more barren but are open for a longer part of the year. The more northern ones such as East Fork, Pine Grove and Rock Creek are more foresty but close earlier. All campgrounds off this road have Rock Creek flowing through them which is great for fishing. Trails are everywhere, lakes are everywhere, and beauty is everywhere. At the bottom of the road is Tom's Place, a general store, bar, and restaurant, and in the summer the small 'town' of rock creek is open. These campsites are heaven in their own right with so many activities so close, but if you want to explore more, Bishop and Mammoth are only about a 40 min drive in each direction (depending on how high up the road you camp).
One recommendation is you call the forest service up there to see which campgrounds are open. Depending on snow pack they can open late or close early. We made that mistake coming to camp in the end of October one year. We were only able to stay 1 night before they closed so we moved on to Pleasant Valley campground.