Satish Dhawan Space Centre (SDSC) in Sriharikota, south of Chennai, is India's main spaceport. They have recently opened up a 5000-seat viewing gallery for launches, complete with a booking system for seats.
However, this unofficial blog suggests that entry is possible for Indian citizens only. Any official sources that can confirm or deny this? Sadly the official site is completely useless, note that the "click here" text isn't even a link...