I'd suggest a cruiser because it would probably be a bit more rugged than road bikes. I don't know how prices go in India but if they are compatible with the US dollar, a bike shop could help you with one to suit you. If you decide to try that, I'd also suggest getting one with derailleur gears and regular brakes. You might not be happy with a single speed bike with a coaster brake. That's the kind where you pedal backwards to brake.
Your budge of Rs.20,000 is equivalent to our $290, and that's approximately what you'd pay in a bike shop for a cruiser with gears.