If you have some, bring Bitbills or physical bitcoins (or both) and a smartphone with the Bitcoin Wallet android client or http://www.webcoin.ch access.  

The sign doesn't hurt, but the physical bitcoins are what show that bitcoin is here, now -- ready for us to try using to try and disintermediate the bank.

It's too bad you don't have some casascius coins to take with you...it would have been good to try and buy things *other than dollars* with those coins (a cup of coffee from someone, a newspaper, anything you might need or want while you're there).  Some of the more curious people might be willing to obtain and then trade such things with you in exchange for the casascius coins (and a card point to bitcoin info).