If its his first time in India i'd recommend a trip down to Goa for a few days. Think of it as kind of India-lite. Lots of foreign people and food, lots of english spoken, comforts of home etc. Then he can dome back and tackle Mumbai properly before catching the train to Bangalore. If he's a real train fanatic (as I am) he can't go past the train journey from Mumbai to Goa in terms of scenery; its fantastic and quite cheap too.