I live outside of San Diego and I take my knitting to the beach in Oceanside all the time. Nothing complicated or delicate, usually a discloth or something of the like.
I just moved out here in October and I remember when the idea of bringing knitting to the beach. I thought nah, it will just get messed up...but the sand comes right off. I am so glad I dared to knit at the beach!
I LURVE knitting on the beach...it is beyond relaxing and just nice. I look at it as a productive way to get a tan