Legal Question in Family Law in California

You do still need an order, but with a signed agreement it should be pretty easy to obtain. You don't really need it done before you leave as long as there is no reason to believe your ex will try to pull a fast one and claim an illegal move away. You really should dot your "i's" and cross your "t's" though, and that means not just having your agreement but also obtaining a custody and support modification order acknowledging and approving the changes. A mediator should be able to do it for you fairly quickly and easily since you are cooperating.