Anybody trying to drive PCH into Malibu today, I can tell you already, that you need to cancel your plans.
This is the heaviest and longest duration rainfall I remember. It's long overdue, just like the drought/rain cycle you mentioned. The water is running into the sewers and straight on to the Los Angeles River/viaduct then onward to the ocean.
I used to hate it when that route got shut down; I worked in Brentwood (West Los Angeles) and commuted north via the Sepulveda Impasse.....when the coastal commuters had to take the long way around, they'd join the already clogged 405 and we'd just inch along.
It sucked then, and I'm sure it sucks more now, two and a half years later.