The official StarCraft II System Requirements says "Broadband Internet connection".
But how many kbps are required for playing online?
Arqade is a question and answer site for passionate videogamers on all platforms. It only takes a minute to sign up.
Sign up to join this community1mbit minimum or 3mbit recommended:
Also note that latency is usually more important than bandwidth.
Games rarely require more than few KB/s.
The latency and stability is much more important. If you are getting more than 150 ms or dropping more than 5% of packets, then it might be a problem.