You can pay the entry fee online to access the beach, which is generally clean with only a small amount of litter like a crushed coke can and some seaweeds. There are many people playing volleyball on the courts, and most surfers hang out near Second Spot, which is just a bit north of the Main Lifeguard Tower. I saw one lifeguard on duty picking up the orange traffic cones off of Thor's Hammer, which is the embankment from the San Juan Creek. It's a very family-friendly beach, but I would recommend bringing a jacket because of the wind from the ocean.
On the northern part of Doheny State Beach (DSB), there are plenty of picnic tables and trashcans, as well as a fairly large patch of green grass. We walked around the bike path to avoid stepping on the beautiful lawn. They also have horseshoe tosses available. We noticed many electric bikes passing by us and onto the sandy beach. Only service dogs are allowed, and they must be on a leash and attended by an adult.
In the north parking lot, there were RVs. After doing some internet research, we found out that DSB is a "dry" camping ground, meaning there are no electric or water connections. There is a snack bar called Doho Cafe where you can order your food and drinks online. They also offer bike rentals, which is a great way to explore the entire park.
The restroom has an open skylight and is very clean. It seems to have shower stalls, although there are no shower heads (maybe they are dressing rooms?). However, there is a shower head outside of the restroom to wash the sand off your feet.
Overall, I would definitely visit again during the off-season. Enjoy!