Since it is a bit hot in the month of May in most of the India, You should try going to the hilly areas of north or north eastern India.
Now you have 2 options in this, either you can go to famous hill stations like Shimla, Manali, Darjeeling, Rishikesh etc. where you will feel a good crowd.
or you can choose adventure trips to less crowded cities like Spiti, leh, Bhaderwah (in Jammu) etc. if you are interested in treks, there are a lot of them in the state of Himachal Pradesh like 1. Triund trek
2. Kheerganga trek
3. Parvati valley trek