On your downtime, you would go to one of those locations and join the group already there, or loiter a little while until someone you knew showed up. If nobody showed up, you'd drift to one of the other locations and do the same thing. One out of 20 times you'd go home without seeing anybody that you were interested in hanging out with.
That's how a commons works, I think. The problem is a lack of a commons, and a suspicion of people in public who aren't currently in the process of shopping. The idea that in this alienated time I'd go to a particular restaurant where people go, drink coffee and just wait for somebody to show up that wanted to hang out almost sounds utopian or suspiciously foreign, but it was my life from probably age 12 to 24.