Parking is $15 per day in the beach-parking lots between Pacific Coast Highway and the beach. If you're able to park near the pier (harder on weekends or special events like the surfing championship end of July), then you can walk to downtown HB and eat or shop.
There is a lot of parking total but it gets more crowded the closer you get to the pier/downtown. All of the beach is wide and open for everyone.
PHXscuba