More likely “yes”
I guess it depends on how you are traveling. Tent camping is likely less crucial to have a reservation.
I have been there 5-6 times and depending on local events, it was wide open.
The one time I had a camper, the spaces were more limited.
The spaces are not all created equal. The tent spots along the creek are more desired as well as the RV Camper sites.
My favored 2 spots have usually been open. They are along the creek and are near bathrooms, but not too close. They all have “renegade” electrical outlets. Basically you can plug in a phone or charger into a light pole on the down low while at camp. They are also shaded in the right times of day. I don’t care about shade in the late evening or early morning. But I prefer not having the sun beat on me after getting back from riding at 4:30 to 6pm and having to wait to take a shower or start cooking dinner.
The website and attendants when you call are usually really good. Ask them how booked they are.