Mid-day should not be too bad on the 405. Take 101 to 405 to 5. That may indeed be best route if it is indeed midday.

I can assure you that going through downtown as someone suggested you will encounter some traffic in downtown. It coud be between 15, 20 to 30 minutes delay going that route.

I take the 405 all the time. Midday is least traffic, so I would suggest 101 to 405 to 5.

But you would have to leave Santa Barbara by 10 am or 11 am as it would take you aboutt an hour to hour to get to 405.