Just in case you find the iOS 6 beta too buggy or just missing your jailbreak, a tweet from Cydia developer @FreeManRepo tells us how to downgrade.
Step 1: Download the 5.1.1 IPSW for you device
Step 2: Put your device in DFU mode
Step 3: Windows users use “Shift+Restore” - Mac users use “Option+Restore
Step 4: Profit