I recommend Telugu to begin with, but at some stage, the school might introduce Hindi also to the kids (may be as a third language). For the kid to face the real world upto +2, Telugu is a must. Picking up Hindi is not going to be that difficult after sometime. But once, if you do not opt for Telugu, it is Tata Bye Bye for our mother tongue.
Yes, what is said previous is correct... But if you want to shift anywhere in India then you have to think it again..
According to me, Hindi is the best option. Since your mother tounge is Telugu, your son can anyway speak Telugu.
@ravi: Learning a new language always helps a child.Mastery of grammar for any language is the key to learning language.
speaking telugu at home and getting taught at school will improve his overall fundamentals of learning a language as he would be also taught about the same for english language which is not his mother tongue.
He would find it easy to master hindi at a later stage since in hyderabad he would anyways pick it up from his friends as he grows up.
Learning the language fundamentally from the roots at an early stage will always help a child to pick up another foreign language easily.
Learning a language and speaking are two different things so you can ponder on it and take a decision.