I do believe they exist in CA, but its not like they advertise, many Amish sects want to be left alone. In Wisconsin we have a lot of Amish communities. Some are friendlier toward outsiders, others would prefer to be left alone. Some actually have electricity and cars, but they use them modestly. I often get to see a few Amish people, as they frequent a farm supply store near my house.

Here is a good sight to start learning about them. http://www.religioustolerance.org/amish.htm

You can find a lot of information with web searchs, just use your best judgement as to which sites are truthful and have good information.