Best time is April-May.
1. School and college holidays
2. ODIs and Test Cricket cannot be played in India at that time of the year
3. Least chance of rain interruptions in Summer
The biggest positive I saw of this year's IPL - Its far more fun in bigger grounds. Throughly enjoyed how the spinners used it, more so Chahal. I would imagine last match's "missed catch" of Williamson would have been a clear six in Arun Jaitley, Chinnaswamy and Wankhade and that doesn't make for good viewing. Unfortunately, I don't think there is a solution for it either.