Yes, you sure can. However, make sure you entire advertisement is in your NeoSig when posting outside the Art, Spotlight or Premium Boards. This means, nothing in the body of the post or in the NeoHTML is allowed!! Also, keep in mind that you have to be actively participating in the discussion and cannot be bumping the board with the intent to get your NeoSig seen.
Also, remember you cannot advertise your entry offsite for any reason.