Yesterday Apple released the public iOS 6.0 upgrade for the iPhone 4s, iPhone 4, iPhone 3GS, and iPod Touch 4G, iPad 2, and iPad 3. We recommend you don’t update as current jailbreaks are limited on newer software versions. You can still downgrade now while Apple is signing 5.1.1, however they could stop at any moment.
1. Download your respective devices 5.1.1 firmware.
2. Plug in your device.
4. Open iTunes click on your device and hold alt on Mac or shift on Windows while clicking the restore button.
5. Find the firmware obtained in step 1.
6. Your device will restore to 5.1.1.
7. You can jailbreak 5.1.1 untethered here.