The best way to find out the download speed would be check out someones connection in your own locality because if some one here says they get xyz speed they might be living right next to the exchange where one would get maximum speed and on the other hand some one getting very low speed might be living 10 kilometres away and in that case bsnl is not at fault atall.

Check out what people on your street get and expect something similar when your connection is up and running.