Yes, I recommend that everyone have a Living Will. I shake my head every time I hear the story of Terri Schiavo, the young lady who mysteriously collapsed one day in 1990 and soon fell into a permanent "locked in state." Her ex-husband wants to remove her feeding tube while her parents adamantly oppose it. I can't help but ask the question, "What would Terri have wanted?" I don't know the answer to this question. In fact, nobody does because Terri never prepared a Living Will. If she had, much of this controversy could have been averted.
A Living Will, also called an Advance Health Care Directive, is a document that appoints an agent to make end-of-life decisions for you in the event you are in a persistent vegetative state or an irreversible coma. It's not euthanasia, which is against the law in California.
A Living Will allows you to give somebody you trust (i.e. the agent) the authority to make a life or death decision consistent with your values. Living Wills have been upheld in California and are increasing in popularity due to highly publicized cases like the Schiavo one.
The cost of a Living Will is relatively small. Additionally, I typically prepare one as part of a Living Trust. In fact, out of every ten trusts I prepare, nine of my clients ask me to include the Living Will as part of their estate planning documents.