Well... the cheapest places to eat are the street vendors...
Regarding France... They have such a downpour of tourists that they are all just fed up about it, it would seem... Don't worry about them being petty and not very fourthcoming... They deal with asshats all day long in their own minds... If you suddenly speak their language that all changes in a flash... Really a shame they can't give you service if you don't speak french... This mostly applies in Paris.
Read up on Prague before going there
