It is much more complicated than this. Yes there are a lot of flags but there are also lots of places where there are no flags.

In my building in Barcelona there are 10 flats. 2 flats have occupants who speak Catalan as the mother tongue, 4 flats with occupants who speak Spanish as their mother tongue and 2 flats with foreign languages.

The language divide isn't always an indicator of their views, in the building there are Spanish speakers who want to vote yes, Catalan speakers that will vote no and a general consensus that everyone would just like the legal option to vote regardless of yes/no leanings.