Generally yes. When the at-fault driver cannot be identified, your own UM coverage is often the only realistic source of compensation for your injuries.

No — but insurers are required to offer it, and you must reject it in writing. Given how many Southern California drivers carry no insurance or bare minimums, declining it leaves you unprotected in the most common worst-case scenario.

No. UM/UIM coverage must be on your policy before the crash happens. It cannot be added retroactively, which is why reviewing your policy now matters.