I snagged a last-minute cancelation in Pinnacles during peak time in May. We were in site 82 of Loop D, which is the RV area. The campground recently renumbered its sites, so that can be confusing if you're researching sites.
Very open and flat. We pitched out tent where you'd normally park and just put the car slightly to the side. Plenty of room. You can buy wood from the camp host, who then delivers it to your site.
We brought a pop up, which was useful over our table during the day, when it got into the 80s. You can watch condors and turkey vultures circle over the hillside nearby. (Learn to tell the difference! Both have red heads, but condors are much larger, have a different white striping underneath and don't flap their wings. If it's big and smooth flying, it's probably a condor.)
Our biggest issue was our neighbor in their shiny silver trailer, who ran their heater/ac all night, which cycled loudly on and off next to our tent. Had it not been for that, it would have been a more pleasant stay. On the plus side, we used a converter to plug into the power box at our site and were able to set up a little cell phone charging station. (The regular power outlet like the kind you see in your house seemed to be blocked, as I've seen it at other campgrounds, as well.)
Not much shade though. We had one tree by our site. Bathrooms were a bit of a walk, but were fine. Water spigot was literally AT our site, next to our fire pit. So we got to say hello to lots of folks. We grabbed an ice cream from the market by the tiny visitor's center at the entrance to the campground. We didn't use the swimming pool or showers.
Tent sites near the water across the way seemed more private, but also more prone to mosquitoes. It was nice listening to the frogs in that area, but that could annoy some people.
Main hiking trail parking lot filled by 8am or 8:30am on weekends during peak times, so we got up there early. They close the road out in front of the campground when those lots fill. So if you see that, you can wait until a car comes down or you can tack on some extra mileage and hike up from the back side of the campground.