I had a favorite coffee shop in California. One old guy used to be there every day for an hour or two, he was bigtime trader, he made his living at it at least. Not daytrading exactly, seemingly more like swing trader. He wasn't exactly a mechanical trader, very superstitious actually. He wouldn't bathe sometimes, said it was bad luck! He'd smell bad leading up to FOMC meetings.. He never shared much with me, I was working on software and algo trading, he was interested but never intruded on me. I never intruded on him. He was interesting guy, drove a very nice car as I recall, dressed well too... Regarding the wifi security you can encrypt the last mile...
I love coffee shops, I can't work at home sometimes, same boring shit all day, people asking me to do some stupid things for them, lots of useless noise from people that don't value quiet, goddam tv's going when nobody is watching them... these are all adults past middle aged too, stupider than little kids... usually people in coffee shops have triple digit iq's...