I'll be traveling with my DV visa soon, so went to pay my 220USD green card handling/issuance fee on USCIS' page. After paying the fee I got the option of creating a profile in the USCIS system (my USCIS) - and in that profile, it is possible to edit one's U.S. Mailing address (and add a physical address). So if I wanted to edit it even after entering at POE I could do that. It looks like I can also monitor the status of my processes with USCIS (I551 card production/shipment) via the profile. Neat!