I am a business traveler in Mumbai at the moment for a 3 week trip. I have my Magellan 210 with me and it worked just now as I walked onto the roof of the hotel and picked up 8 satellites. It works here in India just as it does anywhere else in the world.
However, for the number of people in India there are VERY FEW GC sites. I only found one in all of the Mumbai area which I will try to visit some time this trip if possible.
I am also considering creating some caches of my own but am worried about how I can avoid them getting disturbed by muggles.
As for getting GPS units, you can surely get them from specialty electronics or sports stores, but I imagine they will probably be fairly pricy here and there apparently does not seem to be much of a market for them...