I have visited Hampi, Munnar and Alleppey. all three have different specialities. Hampi is famous for monuments and temples but city itself is beautiful. also it is good for bachelors especially the hippie island. Munnar is famous for tea plantation and beautiful views. i feel for bachelors Alleppey will be better choice. there are clean beaches, clear sky, and good food. also you can enjoy overnight stay on houseboat.
Hey Naivedya, you can visit Pondicherry. It's safe, quite and clean! It's recommended to visit on the weekdays to avoid a lot of crowd. Get good liquor at cheap price and have a nice time by the waters! You can connect with me for more details or if you need any help planning an itineary.