@paulmal nice to meet you!
I'm a neighbor from downstate, and you have many choices. Are you in SLO itself, or in the surrounding county areas? That might make a difference with some plants.
I used to manage a garden shop and my staff and I really tried to help people solve their problems as much as we could.
You have many choices, and some are more ideal than others depending on circumstances. Rose of Sharon and crape myrtle are great, though the mytles will tend to mildew near the ocean, if that's where you are. They're also deciduous.
The king of the fast growing hedges that's evergreen is Ligustrum texanum, Texas privet. (Hmm. It's not called that officially any more. But it's all over in garden shops.) It's fast, evergreen, deep green, and takes lots of heat and sun and can suffer drought for a while, which will, alas, become more and more important I think. It clips up into a nice green screen. Some people don't like the flowers or the purple berries that follow them (the birds love the berries!); maybe tell us more about what your dream hedge is?
There's many choices, all with upsides and downsides. If you have the time, take the time and look with care and don't rush into things.
If you have questions, ask!
Nice to meet you!