Silver Strand State Beach California- HELP

We have reservation to stay at Silver Strand State Beach on Coronado Island, San Diego Ca. Late June. My question is, We had to break up our stay, we are staying in one site one night and then moving to another site to get the nights we need. BUT we could not get one night in the middle of those nights. And we are waiting to hopefully find a cancellation. IF a site does not open up. Where do you suggest we go for one night?