I know you have to download the armor to get it in ME2 but in ME3, I've seen people just buy it off of merchants. The armor looks awesome and I can't connect to live so please tell me its availiable with retail instead code.
Cerberus Armor is not DLC in Mass Effect 3 - you can purchase it from merchants in the Citadel as soon as you have access to the Presidium. It's one of several complete armor "sets" available.
I never owned any of the DLC in Mass Effect 2, (and I didn't have access to the Cerberus Network) but I was still able to purchase this armor in Mass Effect 3.