I had to look up "Breslau". I've been to Wroclaw a few times and never heard it called that. (I live in "Ochseford"!)
Breslau is still used in German, even on road signs. Usually you'll see Breslau (Wrocław) on signs, along with things like Stettin (Szczecin) or Reichenberg (Liberec).
Fun fact: Breslau is really just a corruption of the older name Wrocisław. It became recorded as Wrezlaw in Latin, later becoming Breslau. -Wr got changed to -Br (as this is what the Germans heard), and "zlaw" became "slau". So it's not that there's different names, but rather just two different ways of writing the same name.
The city was founded by Poles (sort of. Maybe pre-Poles is more accurate).
Generally speaking, it's probably correct to say that it was founded by Poles. Mieszko (who led the conquering of Silesia and Wrocław) was the leader of the Polanie from Greater Poland (literally: people of the fields, 'pole' being 'field' in many Slavic languages, and Greater Poland is very flat), and pre-Polish Wrocław was nothing much more than the modern day Cathedral Island. The general belief is that the city was founded around 945 by Czechs, but there's no real evidence one way or another for who actually did.