This Friday, one of my buddies had a couple of friends from college visit him. We met the girls for dinner, and then went to a billiards bar downtown around 9PM. When we walked in, there were about 100 people there, but you could hear a pin drop! It was like walking into a sea of silence. About the time we realized how quiet it was, we noticed just about everybody in the crowd was talking in sign language! There’s a school for the deaf here in town, so either a school event had just finished, or there was some type of conference in town. It was one of the neatest things I’ve ever seen, and I think there were only two other groups besides us who weren’t communicating via sign.
It was pretty neat, just thought I’d share 
It is awesome, if a bit offputting for those who don’t use sign language. One of my cousins is deaf, and it can be a bit unnerving to walk into his house, where everyone other than I knows sign language. Even babies too young to speak can ask their mommy - who is the lady with the fire hair?
You might have walked into a ‘Signing Social.’
There are at least 5 ongoing socials in Santa Rosa that I can think of, some at bars, some at coffee houses, some at restaurants. They’re just different ways for the deaf community to come together and, well, be social.
My husband and I took an ASL class a couple of years ago and went to one (Deaf Pizza - every 3rd Thursday at a Round Table in town) to practice with the community. Everyone was very helpful and inviting, and you’re right, it is a neat experience to walk into a packed restaurant and have it be nearly completely silent.
We’re currently taking an Enology class together on Thursday nights and happened to stop into the Round Table where Deaf Pizza is held a few weeks ago after class. Unfortunately we realized pretty quickly we have forgotten much of what we learned.