You "don't" communicate with the person your playing with.
There is no way in-game to sync groups up so you can have a bigger game. It's luck of the draw. Maybe there is something the in game friends list that might help you re-join a dropped game, but as it stands, it's messy. Once you're playing it's pretty good, even when playing with people on the other side of the world, but the organizational aspect has a lot left to be desired. It's an ok system if you want to have massive random games or small group of friends that know each other explicitly, but whatever is in between gets lost like what happened on Wi-Fi night.
There were about 3 groups playing battle, but the games never got bigger than 4 people. NWR chat is going to be a must for our current group size.