If the damage is only occurring at night, it ounds like snails or slugs, which
are quite abundant in California. Go out with a flashlight when it's dark and
you might find them munching.
You can put out a few saucers of beer. They like it and they drown in it; or
you can just do nightly raids and collect them and put them in the trash can.
If you're getting daytime chewing, you might have some grasshoppers. That's
what's been chewing on my veggies the past week or so, here in Central Florida.

Regards,
June