Go where you feel most alive !!
Best time to visit Prashar lake, Mandi is from end of December to February. It is located around 50kms from Mandi in Himachal Pradesh
If you are going alone then you can book a bus from Majnu ka Tila in Delhi to Mandi, it would take around 10-11 hours & cost you around INR 800 (Start around 20:00 & reach by 7:00).
If you are going in a group it would be best to book a cab which would cost you nearly about INR 9k-10k plus it gives you flexibility of timing & covers the cost till trek & post trek.