In reply to fluff woolley:
Yes, you can camp at the Buttermilks; not near the boulders themselves, but there are a few pullouts on the road up. There's no water and, until recently, no toilet facilities.
It will still be quite warm and there is no shade in that area, so you might like to explore some of the camping options either a little higher up the road, or further north towards Mammoth where there is tree cover; there are numerous options on the 395 between Bishop and Mammoth