Mutts quote about entering the USA is correct. However you will be returning which is different as Backpacker explaned.
Despite ESTA having been in place since May 2009 the green card was still issued to us last year.
Yes you will have to register with eAPIS but it is fairly straightforard and free. ESTA renewal was $14.
The only question is, are the rules the same for Canada as the Bahamas.
I'm off there again in three weeks with my visa waver/ESTA for the tenth time.
D.O.