I am one of many waiting for a JB for ipad 2 iOS 6. Does Cydia auto save SSH blobs from previous iOS? If so, how does one downgrade to 5.1.1? If Cydia doesn't, how do I save my blobs for the future?
Yes - Cydia saves blobs. Kind of. In order for it to save blobs, you (1) must be jail broken and (2) visit Cydia after the jail break in order for it to save blobs. If you don't jail break or don't visit Cydia, then no, the blobs are not auto-saved.
What most people do is run a program called Tiny Umbrella. You run this every time it's updated (and/or every time there is a new iOS version). If Tiny Umbrella is run for every version of iOS - when it's current and signed by Apple - then you'll have saved blobs. See this for more on blobs: http://www.ipadforums.net/showthread.php?t=59291
That FAQ I linked also tells you how to start saving blobs for the future.
As far as downgrading to iOS 5.1.1 - unless you have blobs for both iOS 4 (any version) and iOS 5.1.1, I'm afraid you can't downgrade. If you don't have the blobs now, you can't ever get them.