So the link is https://beta.guildwars2.com/
You can sign up for the beta but the catch is that its limited for 48 hours so you either do it in 48 hours or you don't do it all.
The Guild Wars 2 beta-sign-up page is live! The page will be open for 48 hours, so sign-up for a chance to get in, and spread the word! https://beta.guildwars2.com/ ~RB