Starcraft II release date is still on July 27th, but you can already start download the game since now. However, you can only launch it starts on July 27th and of course you must pay-up before playing.
But it’s still advised to download now, because lots of people will try to download on the launching day and cause the server got a heavy load. So you’d better start download Starcraft II now. Download it on the link below. You must have a Battle.Net id first. Don’t worry, it’s free.