SuperBot and SCEE will be opening up PlayStation All-Stars Battle Royale to the public in September, but for a limited time only. The beta test will be across both the PS3 and PS Vita between September 11th and September 18th 2012. The beta is opt-in, so you will need to sign-up for a chance to get access before the game is released.
If you want to register interest in the beta, head over to the PSN Beta site and complete the sign-up process. Participants who get chosen will get an email with instructions on how to get their voucher to download the beta client.