I started downloading the Starcraft II Closed Beta installer about three hours ago. The first build is about 1.64GB file size. Some of you will get an email from Blizzard. Beware of fake emails however. Your best bet to find out if the email is accurate is to not click any links. Simply go straight to your Battle.net account page. You will see the Starcraft II icon along the other games you registered in the past. Below you have the screenshots of what to expect in the Battle.net account page.
Sorry for editing out my personal info. =)