Parks in the San Diego/La Jolla area

After the first of the year, we would like to head to Southern California to visit my wife's brother (lives in La Jolla). We expected sticker shock when looking at RV Parks in the area, but $60 - $90 a night and up is a bit much. A neighbor here at the RV Park on Aberdeen Proving Ground recommended Fiddler's Cove on Coronado Island (Navy facility), but they have NO availability for the month of January. The Admiral Baker Field RV Park seems to have availability, but the photos look like closely-spaced RVs circled around a grass field with a playground in the middle. At $30 a night, though, it would be a place to lay our heads down at night. Has anyone had any experience with the Admiral Baker Field park or can you recommend some budget-minded alternatives for about a week in the SD/La Jolla area for the first half of January?

Thanks!

Rob