Not just in California, my area is seeing an increase of cases as well. The Children's Hospital I work for is the only one in the region. We are getting lots of sick kiddos. There is definitely a trend in un-vaxed kiddos and also adults. It's offered for free at postpartum but many still decline. I got mt TDap after having my baby and while it did hurt, it was not any worse that the flu vax.
Also, being so close the the Mexican border, we cannot control all the folks who have never been vaccinated, or have no insurance.
Lately, I have seen many ads in the paper, craigslist, etc; about moms looking for other kids with active chicken pox to 'have a party' with.