There are tons of Motorhomes that make it out to the beach. Most of them do end up getting stuck, though.
Pismo is a good riding, small, but good. My first time riding there was a few weeks ago. The coolest part, for me, was that we were parked 100 feet from the water. The views are something you can't get anywhere else. If you plan on camping, keep in mind they only sell a set number of camping passes, so get there EARLY on Friday to guarantee a camping pass. Someone might correct me, but I believe it's 1000 passes?
Pismo is always packed during the summer months, from what I've heard. It was pretty damn busy when I was there a couple weeks ago.