Haven't stayed at any parks at Pismo, but have rented in the town for a month at a time, once or twice. Mention my name in Harry's and you can get charged extra! Sorry I can't be more help. Look at Grover Beach RV parks.
We are in Morro Strand RV Park in Moro Bay right now, nice park, good flat gravel base. Good bathrooms/shower/laundry. No trees, about 1/4 mile to the beach and a good view of Moro Rock. Full hook-ups. Easy access to walk to the harbor over a dry creek. Moro Strand State Park, just to the north, is fine for a weekend with smaller RV's, a 36 might be on the large size for (tight)available space. No hook-ups, water & dump available. Right on the beach, in winter its exposed to storms. Morro Bay State Park is listed as 35 ft max but they accept larger rv's in pull throughs, water and power, dump station. Under old growth huge trees, right on Morro Bay. So sat reception is poor. About a mile into the town. Launch ramp and marina with kayak/canoe rentals, as well as a good resturant right across the street. Golf course near-by and a pretty nice little museum. About $50 a night.
Campgrounds and Camping Reservations - ReserveAmerica Bay Pines is a smaller RV park, spaces seem tight to me, I think it has a hot tub, no view of the bay or the Rock. Morro Dunes RV Park is closest to the rock and beach, haven't stayed there, but wouldn't hesitate at all.
No parks in SLO, there is a KOA in Avila Beach, but have heard very mixed reviews. At Port San Luis, on the bay, there are some good sites for weekend camping. Don't know much about them, most seem to be dry camps, think the county of San Luis Obispo runs them, they are between the road and the shore. Currently most are occupied because of the Diablo Canyon Power Plant outage, but most of the contractors will be released the last week in October, so November is do-able. Check the SLO county website for details. Weekends can be rough to get reservations, since a lot of people of the fishing persuasion like them.