The following is an outline on the law in alabama:
Notary: Although the Alabama statutes do not explicitly state that a power of attorney must be notarized to be effective, it is highly recommended that any power of attorney created in Alabama be notarized.
Witnesses: No requirement that the signature of the principal be witnessed.
Signature of Agent: No requirement that the agent sign the POA; however, the standard MedLawPlus.com® POA form does have a signature block for the agent. It is a recommended practice to have an agent (also called "attorney-in-fact") sign the POA.
You should have the POA witnessed and notarized to avoid any difficulties, regardless.
Disclaimer The above is not to be considered as legal advice. You should meet with a qualified attorney for advice based on the specific facts and law which apply to your case. The above does not establish an attorney client relationship.