If you've ever driven north on I-5 just before exiting to Disneyland (I was born in San Diego), you'll notice some very interesting road sign coincidences: exits to Main Street, Highway 55 and 17th street.
Main Street is for Main Street in Santa Ana. You should drive down it some time. There are wonderful old buildings you can see as you drive through downtown Santa Ana and the various government buildings for the county of Orange.
Main Street will take you all the way to Irvine, but there it is the usual cookie-cutter houses Irvine is famous for.