Well, I have experience with both alcohol and grass. I drink daily and smoke daily, I have been banded for 3 years, I am at my goal weight for the most part. My band is filled and eating is slow, I actually should have some taken out so that I can eat more whole foods and stop eating so much processed junk food.
Anyhow, drinking is something that I have no problem with, I am able to drink one after another all day, beer, mixed drinks, whatever. Now I do have to remind myself to eat because I often skip Breakfast and sometimes have a drink before eating anything for the day but I still drink about half my calories ~1600-2200+ a day in alcohol. (Probably not recommended for everyone.) Be careful of too much carbonation in the first months especially while you are healing and still careful after that too prevent stretching of the band. TIP: I sometimes open a beer and leave in the refrigerator for a couple hours before I drink it to knock some of the carbonation down.
As far as reefer goes, it actually helps my belly settle after a large meal, or while eating sometimes I get a little backed up. A toke off the pipe VERY MUCH helps with instant digestion, especially if you cough a little.
Hope that helps, peace brother.