Rain or shine, we'll be there. The afternoon meet is at Fantasia Gardens (which is covered). Most of the rides are indoors. And the Noon Meet and Morning meets are outside, so bring an umbrella and dress warm if they say it is going to rain.
But rain in SoCal tends to be light and spotty. So we aren't worried.
In a way, I hope it does rain so we'll have the whole park to ourselves!