My address is:
Gunterman, John
PRG 6-1-2
APO AE 09354-3005
I believe some bases/posts have thier own mail facilities, and if yours does you can ship it "APO to APO" for free.
If you need to go to the post office as for what we call Space Availible Mail ("SAM") it is like parcel post but a bit cheaper still, is more than sifficient. Dont pay for Prioirty, I'll be here for 11 more months, I don't need anything that fast (or expensive).