In Rishikesh, most of those with whom you will communicate well speak English. The rest speak the second official language of India – Hindi.
If you come to India to practice yoga, it is worth bearing in mind that the local style of teaching is different from the West, local teachers give a lot of instructions, and to understand and correctly perform the exercises a little good to speak English, you still need to understand the Indian accent. It is also good to know the names of asanas in Sanskrit, but if you do not know – do not worry – just do what others do.
As for communication on the street, below is a small dictionary of useful words and expressions.
Rishikesh is ancient Indian city in the footprints of Himalayas, now widely knows as Yoga Capital of the World