[tedmiston]

My experiences have been consistent with yours. Though if I really have hard work to do in a coffee shop, I'll put in headphones. In the office we have a "don't interrupt someone wearing headphones" rule (it still happens once or twice a day), but that seems to be a good signal to people in a coffee shop as well.

[mafribe]

Good point.

It requires a bit of social acuity to understand who's really focussed and doesn't want to be disturbed, and who'd be quite happy for a pleasant chat.

An easy trick to gather intelligence on what they are doing before initiating a conversation, is to walk past them, maybe to get a drink or on the way to the bathroom, and glance at their screen. If you see the familiar colours of Facebook, Twitter, Reddit, YouTube or other time-sinks -- and they are on display surprisingly often -- you can be reasonably sure that your approach will be well received.

Body language gives clues too ... bobbing along to a rhythm? ... no, they are not working on P vs NP or the latestst deep neural net convolutional reinforcement learning ... And if you can hear the music emanating from their headphones they aren't highly alert to a job requiring deep thinking either.

[tedmiston]

That's also a good point.

The other day I went to my neighborhood coffee shop an hour before work to just have a coffee, sit, and reflect. No computer, just me and a pour over.

I jumped into conversation with a few others at the bar. Sometimes I forget one can be in a coffee shop without a screen. It was much easier to focus on conversation and sensual things like the tasting notes of my coffee, instead of the nagging fomo of email and social notifications.