First off, anyone that compares smoking pot to smoking crack is probably on crack. And as far as the legality of it, I have yet to hear a decent argument for it even being illegal. It is less dangerous than alcohol and has a 0% OD rate. As Dr. King said, "We have a moral obligation to disobey unjust laws". Now with that out of the way... :-)
My biggest problem with smoking pre-op was that I would get some serious munchies. In a way I thought banding might fix that, not that weed munchies is the reason I got banded or anything. I just thought it would be a nice side effect of the band. I tried it a couple of weeks after surgery and I got some SERIOUS munchies. I didn't pig out or anything but I did eat more than I probably should have and I'm lucky I didn't cause slippage. I would be careful with it, just make sure there are no munchies around the first time you try. Everyone is affected differently, and I found out that even though I couldn't eat a lot that didn't keep me from wanting to. Good luck :-)