Actually, the post office recognizes either QC or STV, but some prefer to use one or the other depending on thier views of incorporation.
I use Queen Creek since it is the address when I purchased the house and I refuse to associate myself with the proposed incorporation. I do not want to be associated with any political official who misuses funds to create signage for a city that is not in existence yet. County funds should not be used for the STV signs since we are not "the city of STV".
Just my opinion, but as far as your mail, etc.... either one is valid. :)