So, I've spoken with the school and my new address has been confirmed- I can start using it whenever. I know I've spread around a few different dates as to when the switch should occur... Basically, it comes down to this.
Penpals in the USA: I would switch somewhere between the 14th and 16th of August. However, if you're not in as big a hurry to get a reply back and you want to send a letter to my new address a little early, it'll make my day to find mail waiting when I get there!
International Penpals: The same goes for you, if you want to surprise me and aren't in a big hurry to hear back. However, the latest date you should switch would be August 12th.
A reminder: if you DON'T have my new address, please leave a comment or email me at firstname.lastname@example.org and I'll get back to you as quickly as possible. Thanks!