Well, there's now proof (if proof were required) from a research project in the Victoria University in New Zealand, which
...found that listening to the sound patterns of a new language set up structures in the brain required to learn a different tongue.
'However crazy it might sound, just listening to the language, even though you don't understand it, is critical,' study author Dr Paul Sulzberger said.
'Our ability to learn new words is directly related to how often we have been exposed to the particular combinations of the sounds which make up the words.
This basically means that you should not worry if the learner is not understanding Kannada. Understanding a language always starts with the state of not understanding. Doesn't it? If Kannadigas persist in talking in Kannada even in front of a non-Kannadiga, unbelievable changes happen in the learner. As the study says,
'Neural tissue required to learn and understand a new language will develop automatically from simple exposure to the language - which is how babies learn their first language'
So go ahead, try it (if you aren't already doing it)! It's not being impolite. It's just being proud and scientific-minded and having the will to carry out your own conviction about the status of Kannada in Karnataka, and to help migrant non-Kannadigas integrate into this great land of ours.
So, let Kannada be heard by them first. Only then shall you have the pleasure of hearing Kannada from them.