I have a client that currently lives in Cayucos. In a recent conversation, he said that when it is foggy in Morro Bay, it is not foggy in Cayucos. If you look at Cayucos on a map that makes sense, as Cayucos is on the protected north edge of the ocean basin.
You can look up staticicis about precipitation online on several weather related web sites. For example http://ca.rand.org,
but you will need to register. The closest weather station is located in Morro Bay, so it may be difficult to find accurate statistics about Cayucos. If you are serious about finding weather information, I would suggest going to Cayucos and talk with people that live there. Let me know if my answer helps, if not feel free to contact me again or call me at 805-471-0828. David