Whether or not you ride in the rain depends on whether you're prepared, and how hard it's raining. Out here in southern LA (Cajun country, not Cali) it doesn't rain often, but when it does it pours, and visibility is near zilch. If you're carrying anything, it needs to be in something waterproof, like putting your clothes in large gallon zip-locks. It also depends on whether using your car is an option... I know I'd be tempted to take the car if it were pouring outside, so you need to decide beforehand if that's something you can live with. For me, it wouldn't be bad, because it only rains on my commute maybe once a month.

I'm working on rain-worthying my bike so it won't ruin my day if I get caught. You know what the Boy Scouts say: "Be Prepared."