If you fancy that sort of thing, there is a great "workers canteen" not too far from Wenceslas Sq.
Its like school dinners, you buy 3 tickets, one for a starter, one for a main meal, one for a dessert.
You carry your tray and hand it in to each of the three serveries .
Proper local food.
If its a weekend, avoid Wenceslas sq as you will be hounded by pimps suggesting certain bars, sex shops , drugs etc