From Hitler's Table Talk (March 7, 1942):

The English language lacks the ability to express thoughts that surpass the order of concrete things. It's because the German language has this ability that Germany is the country of thinkers.
The Italian language is the language of a nation of musicians. I was convinced of this one day at Obersalzberg, where I heard a speech by an Italian blinded in the war. When his speech was translated, nothing was left—a vacuum.

So by his own words (as recorded by his closest underlings), he could not speak Italian. He does appear to have a rudimentary understanding of English, but at the same time, this concept of English (that it's a less than eloquent language, if putting is nicely) is a common theme among German nationalists of that period. I don't know much about Austrian schooling, but both in Germany and the Netherlands, a student would have at least been introduced to at lest French and English (in the Netherlands also likely German) during their school years, definitely if they have gone to the Gymnasium or Oberrealschule. Hitler did go to the Realschule, but I'm not familiar enough with the Austrian system at that time to know if that would directly equate. He was very likely exposed to it though. Also, because he was raised Catholic in pre-Vatican II days, he would have been exposed to Latin. Whether he could do more than recite a few basic statements though is up for debate.

I can't find any references to it in the Table Talk, but I've read sources that say it's there. Alas, my wife just got home, so I gots to go.

This makes me wonder- how did Stalin communicate with Churchill and Roosevelt at Tehran?

Mussolini could speak German and French.