Blizzard said this: “Starting that day, gamers with a thirst for fast-paced action and adventure will be able to purchase Diablo III at retailers throughout the United States, Canada, Europe, South Korea, Southeast Asia, Australia, New Zealand, and the regions of Taiwan, Hong Kong, and Macau. In addition, gamers in the regions above as well as in Mexico, Argentina, Chile, and Brazil will be able to buy Diablo III digitally via Blizzard’s Battle.net® website.” The Russian version of the game is delayed until June 7th.

So that is who can buy Diablo III on 15th of May.