First and foremost, bonfires MUST be kept within the specific Oceanside City fire rings ONLY. You cannot bring your own bonfire pit. With that said, fire pits are dispersed on a first come, first serve basis. I’ve heard rumors of people going to the beach at 3 or 4 am in order to have a claim on the pit for the rest of the day. Granted I’ve only heard that rumor on the 4th of July, but still, that’s early. Fires are only to be burning from 6:00 am – 11:00 pm and there must be a person in attendance at all times the fire is burning. The fires can only be put out with water, absolutely not sand!
The advice I usually give is this: if you plan to have a bonfire in the summer months, it gets pretty competitive to get a ring. (Especially on July 4). There is the highest concentration of fire pits at the north end of the Oceanside Harbor. Once you are at the Oceanside Harbor there are two places to find a pit. The first is on the beach side by the North Jetty. The second is on the east side of the general/RV parking lot at the very north end of the Harbor and those pits face the actual Harbor. There are fire pits at the Pier as well but from my experience, those fill up faster than at the Harbor.
If you plan to have a bonfire any time other than summer, you are typically pretty safe just to show up and find an open bonfire pit. Especially on the north end of the Harbor. Don’t hold me to that, but personally when I have beach bonfires down there in the off months (late September – late April) I do very little planning and always land a fire ring.
PS here is the official link to the information about Oceanside beaches, bonfires included. http://www.ci.oceanside.ca.us/gov/pw/harbor/info/