Legal Question in Civil Litigation in California

I don't see why not as long as at least 60 days have elapsed; a demurrer is a general appearance.

California Code of Civil Procedure sec. 437c says --

(a) (1) A party may move for summary judgment in any action

or proceeding if it is contended that the action has no merit or that

there is no defense to the action or proceeding. The motion may be

made at any time after 60 days have elapsed since the general

appearance in the action or proceeding of each party against whom the

motion is directed or at any earlier time after the general

appearance that the court, with or without notice and upon good cause

shown, may direct.