If you want some nice street food in Panjim there is a good place on 18 June Road. Go past Bombay Bazar and keep walking until you see a long counter with cases of food on it. Can't remember it's name but easy to find.
Pakoras, samaosa, very good bhel puri, veg cutlets, pani pooris and lots of other food as well as drinks.
There is small area inside with a couple of benches so if you don't want to eat in the street you can go in there.