It has been made Canon that Ioania has their own language, and the large majority use it as their primary. To the point when Riven became a Noxus runaway soldier to hide in Ioania, she had to teach herself the language in order to survive so she could work a semi stable job and interact with the locals, for essential reasons.
-Simple hellos and goodbyes
-The normal words you would need to know to survive in a foreign country
That being said though. I do have a major lore question involving Ioania, and hell the game itself.
One thing i dislike about the game, is the fact, every champion in the game, speaks the same language. If you chose the NA server they all speak english. If you chose korea, they all speak Korean.
One problem with that. It has been made Canon, that the countries and kingdoms have their own languages. There is a good chance if you made Olaf meet up with Zed, that they would quite literally only be talking with their fists, and any words would just be pointless as they have no fucking clue what the other is saying.
-What is the global language of the world of LoL, i'm assuming it's whatever Noxus speaks as they are basically the England of the game, going to other countries, conquering and influencing them.
-How many Ioanians could actually have a conversation with a Noxus Citizen.