Camping Aug 3rd...no reservations, suggestions?

[R&G]

Hello,
We would like to go camping Aug. 3rd and are looking for a site up near Mammoth, Sequoia, or Kings Canyon.  We will leave Long Beach after rush hour on the 2nd, and stay in a motel close to the area in order to get to campsites early Friday morning.  

We don't have reservations, but in Tom Stienstra's California Camping book, there are numerous campsites that do not take reservations.  Have any of you shot up there on a thursday night/friday morning and had success with finding a site? Dry camping is absolutely fine with us.

Your feedback would be much appreciated!
-R & G

[R&G]

We have Reservations Aug. 3rd @ Four Jeffrey near Bishop, CA.  Has anyone camped there before?