do I need a license to drive a motorized bicycle in san diego, california?

I’m very interested in getting something like this:
http://www.bicycle-engines.com/49cc-complete-powered-engine-p-156.html
There are other options as well, including an 80cc engine, and such.
I know that scooters, and “motorized bikes” require an M2 license in California. My question is, how many people actually get this [...]