Vince, I believe you are
Sunset Zone 19, which means you get slightly milder frosts and evening temps than Jole. I've actually visited Riverside.
From what I can see of both zones, I think a planting out date of April 1st is plenty conservative. No need to wait until the 3rd week of April. Heck, I'd plant right now if temps are looking stable.
Sunset Zones are much more specific than the USDA Hardiness Zones.
Then there is the Heat Zone Map which helps explain why Zone 8b Seattle and Zone 8b Houston are not even remotely similar in growing conditions or planting calendars. In some Zone 9's you have all summer and into early fall to grow vegetables. In other Zone 9's, vegetables pretty much quit in late June so you have to start early and act as if you were growing in Saskatchewan.