For starters, there is no such thing as "the language" in India. There are more languages here than I care to remember, and most of 'em have nothing in common with each other.

A language that works in Chennai in the South (Tamil) will have no takers in Delhi (Hindi). Similarly the language in Mumbai (Marathi) will have no speakers in Kolkota (Bengali).

The most common lingua franca in India, especially for tourists, is English. Signs are virtually all in English and there is always someone who speaks and understands the language, even in the strangest places.