Our preferred campground is Guajome county park as it's less money than most,a really nice place to stay and close to our GK's in Oceanside. The down side is that is's hard to get into with less than about 6 months notice. The second choice is Paradise by the sea,as it's quiet,close to the ocean and downtown Oceanside. The downside is it's REALLY expensive in the summer and full,but i9t's medium price in the winter.
The next place we've stayed is a brand new one in Vista,but close to Legoland,well several miles,relatively inexpensive and it's called Olive Street RV Resort. They do have a pool and a nice clubhouse.
I did hear a rumour that the Oceanside Elks club was accepting non-members.
Time before this last trip,we wanted to stay at either Carlsbad Beach or San Elijo SPs and found that they were full at the Christmas holidays and when we got down there and drove thru them,they weren't full at all. However,both of them cost more than the winter rates at Paradise by the sea. Carlsbad was $55 and San Elijo was $65.