Pune to mumbai

Mumbai-a city of dreams

1) The best way to reach Mumbai is through train, as it will drop you to Shivaji terminal. From there you can visit gateway of India / Taj hotel/ main tourist spot, which is 2-3 km.
Either you can choose to walk (5min distance) or take a local bus to the Gateway of India

* don't miss to see Shivaji terminal at night, it's amazing and a world heritage site

2) A second option  is to reach Mumbai is through bus. Take a bus from Swargate,Which will drop you to Mumbai west,
It will be a very long journey full of traffic jams and etc.