Hi williamli,

I have the 17-55 and I highly recommend it. Now, if you plan some trips where only one lens can be taken, you might find the 55mm a bit too short. Also, if I were you I wouldn't give up the 17-24 range as 17 isn't that wide on your camera. Therefore, I'd say the 18-135 is a very good choice if you want/need to limit the number of lenses you carry with you.

Let us know what you decide at the end.
Cheers,
S.