To better prepare the servers for the final release of the Diablo III game, Blizzard Entertainment made the decision of allowing players to play the Diablo III beta version this weekend.
So, even if you don’t have a Beta code you will be able to play Diablo III game, for free. But, in order to play the game, you need to create a Battle.net account ( you can create one for free ).
You can only play the Diablo III game from Friday, April 20, 2012 until Monday, April 23, 2012. During this time interval players will be able to choose any character class they want and they can advance up to level 13.
More information about this Diablo III beta session can be found on the official website of the game. The beta client of the Diablo III game can be downloaded here: https://us.battle.net/account/download/index.xml
Diablo III will be released on May 15, 2012, for PC and Mac.