I've watched my daughter in crowds, and don't think she's able to follow more than a couple of signers at once. Not very different from being able to make sense of more than a handful of voices all happening at the same time. Just as she would need to turn her eyes to follow an individual signer in a crowd, so would she need to turn her head to aim her microphones as an individual speaker in order to focus in on that particular conversation.
If we were in an ideal world where all used ASL, yes, a visual language would be GREAT for those inevitable periods of complete deafness that a CI wearer has. But, we're not. While my daughter may be fluent in ASL, very few people are. And unless she limits her interactions to only other signers, without processors on, she'll simply be in the same boat as any unaided deaf person among non-signers with whom knowing ASL doesn't help: finding ways to communicate via speech, speechreading, common gestures, writing, texting.
