Best Practice for "Membership" use on intranet with @ 14 plants

I am using membership to create a news intranet site for a client. They currently have 14 different plants and the corporate office.

I want the ability for a user that is from "plant A" to see "plant A" content and other content to seen by all (usually generated from corp. headquarters; sometimes generated by a plant manager).

I want to keep sign-up for users very simple - and it is free. I'm attempting to avoid having 14 choices on the sign-up page, yet allow a new user to choose which company they are from.

Should I be using "Levels" or "Subscriptions" to achieve the simplest solution to the above?

Thank you for assistance,
Greg (For Carl)