If you're busy working on something on a computer nobody is going to interrupt you. Same with playing on your phone or reading a book. People have an automatic "OCCUPIED: Do not disturb" flag over their heads when they are absorbed in something. Bugging you when you're working on something would be just plain rude.
Go to Starbucks, get a cup of coffee and drink it slowly while you sit and listen to conversations around you. Get a table or booth with a good view of outside so you won't have to stare at the wall. Project an air of "I am relaxing, unwinding and just plain resting and doing nothing at all for a bit." If someone talks to you, great. If nothing happens, you had a good break from the daily grind. (Get it, coffee, grounds, daily grind... sorry, ignore my bad jokes.)