Legal Question in Civil Litigation in California

Did you file a motion to quash service and the judge ruled in your favor? If so, then no you don't need to respond until they serve you properly, unless the court ordered you to.

You might as well respond, because otherwise all you are doing is delaying, forcing the plaintiff to re-serve it and run up further costs you will be charged with. If serious about hiring counsel to help you in this, and if this is in SoCal courts, feel free to contact me.