Quick bit of news, I just learned this now. The Diablo 3 beta will be open to ALL this weekend, except for those that live in Korea.
The Beta will be open from Friday April 20, 2012 at 12:01 PM to Monday April 23, 2012 at 10 AM PDT. You will be able to play as all five classes up to level 13 and to play all you need is a Battle.net account. You can begin downloading the client now from here. Finally, the beta client only comes in three languages (English, French, and German), when Diablo 3 is released it will be in more languages.