Yes, you can select any area, and it doesn't have to be exact. You will need to draw the area though, you cannot import your boundaries.
When you create an area in the MyAccount portal, you're defining a template/metadata for that particular service, at that point no data is downloaded. We recommend that when you are interested in an area you roughly sketch out around that area, it doesn't matter if it is not following your local government area boundaries. The data is only downloaded when you bring it into the application, and you start interacting with the imagery in the application.