Becka,
I'm sure you've probably gotten your answer now but to post an answer to anyone else who may encounter this problem. I also just moved into Castlegate and here is how found out which box was mine..and subsequently how to get a new lock, etc. Information came from very helpful neighbors on my street (Jay Lane). They said to go to the Post Office in Queen Creek ( on Ellsworth, I believe it is) and find out which box was ours ,. The postal worker there gave me the location and box info and then told me I'd have to get it rekeyed if the key I had didn't work. I had a key that I thought "might be" a mailbox key but was not. A helpful neighbor told me to catch the mail lady "Suzi" and ask her what to do. I gave her my address and box location and she got the lock out for me and told me I could go to Home Depot and buy a replacement. Did that, went back the next day and caught her again and she put the new lock in. Voila! now have box with 2 keys for it and am getting mail. Much easier, less expensive than having to call a locksmith and quick. Delighted with my helpful neighbors, six came and introduced themselves the day I was moving in, and with a cooperative post office worker, and postal carrier. So far I'm delighted with the neighbor hood friendliness.