One of my cousins recently graduated from TANUVAS and is a North Indian native. However, he mentions that there were no issues with his stay at the institute. The lectures held mostly are in English since it is one of the mandated languages to connect with natives coming from a number of places, besides Tamil Nadu alone.
The faculty of the institute effectively provides priority to English as the major mode of communication.
Having access to the basic English language is more than sufficient to understand the classes, without any barrier at all. If you are only interested, you can take part in learning quite a bit of Tamil words so as to connect more with the surroundings.
There are several students, who are pursuing the 5-year course, without having to deal with any language barrier at all.