You cannot play with most of us without downloading the multiplayer DLC! It's all free and totals 3 - 4GB, so it's not a fast download depending on your connection. Thanks all ~
Just to make it easier for people to get the DLC, here is the link for the US Web Store. The linked item is a bundle pack with all 5 free multiplayer packs. Just need to sign in, add the item to your cart and 'purchase' the free DLC. From there you can queue it for your console and the next time you turn it out it'll all start downloading. I can seem to figure out how to change web store's region, so if anyone wants to link Europe's equivalent, it'd be nice.