The Medal of Honor beta has been announced in EA's press release, but you have to pre-order Medal of Honor to get your hands on a beta key.

Electronic Arts Inc. announced yesterday during the E3 conference “that Medal of Honor™ is now recruiting players for a massive global multiplayer beta test that starts on June 21. Players will be granted early access to two action-packed maps on the PlayStation®3 computer entertainment system, Xbox 360® videogame and entertainment system and PC. EA also announced today that Battlefield: Bad Company™ 2 VIPs who have pre-ordered Medal of Honor, will be able to enter the multiplayer beta even earlier; starting June 17. Developed by DICE, Medal of Honor multiplayer delivers world-class action and dedicated server support. Beta key distribution details are available at www.medalofhonor.com. The beta maps will be playable this week at the Electronic Entertainment Expo (E3) in EA’s booth located in the South Hall, booth #1601.”

Source: EA press release

But the official site states that you have to pre-order the game to get the beta key:

The Beta is available when you pre-order Medal of Honor. Beta Redemption Keys are available at participating retailers as a reward for pre-ordering Medal of Honor. Once you have a Beta Redemption Key, just go to www.medalofhonor.com/beta to redeem it for a code for the platform of your choice.

Source MOH Website

You could most probably just pre-order MOH now and cancel the pre-order once you have the beta key (if you don't want to order the game just yet) but I can't say whether you'll get charged for it or not, so if you try it, it's at your own risk.

Just ordered it from Play.com

It did say in the E-mail that it won't charge till they distribute it so all good

Also the Xbox Beta Key has been delayed a week