A simple solution to this problem would be to replace the seating in the coffee shop with less comfortable ones.
A while ago I had to work from a coffee shop for one day and while the chair I was sitting on was comfortable for 3 to 4 hours, my back and arms really started to ache after that time. The next day I still felt it.
This would solve the problem: regular laptop hobo's will not use your shop because it will not be comfortable to work there, while customers that are there to socialize are there for a short amount of time anyway.
A while ago I had to work from a coffee shop for one day and while the chair I was sitting on was comfortable for 3 to 4 hours, my back and arms really started to ache after that time. The next day I still felt it.
This would solve the problem: regular laptop hobo's will not use your shop because it will not be comfortable to work there, while customers that are there to socialize are there for a short amount of time anyway.