"A Pact for or against Europe" (pdf).
The translation is published as an afterword in a new book, entitled "What Germany Thinks About Europe" (edited by Ulrike Guérot and Jacqueline Hénard). A German edition of the book is available here (pdf).
The speech was given by Habermas at a meeting on "Europe and the re-discovery of the German nation-state" arranged by the Berlin office of the European Council on Foreign Relations. The original speech is available here (pdf) and here ("Süddeutsche Zeitung", April 7, 2011). Excerpts have been published in "Blätter für deutsche und internationale Politik" (May, 2011).
See reports on Habermas's speech here.