Does this place get full here around this time of year... Does one have to make reservations?

yes. you’ll need reservations.

I would 100% recommend reservations. Most CA campgrounds are full months in advance.

I was there last week. They are filming a movie on site. Weekends it was full week days M-T it's hit or miss. Get there by noon if you don't have reservations.

Yes you should to be safe