64 oz yikes!
I was a water drinker pre-op (although not consistent with amounts, usually not enough), so I didn't have to quit sodas or juices which is nice. if you haven't already, switch all your daily beverages to water.
getting a good water bottle with markings is key, I have a 24oz one, and I drink about 3 a day now post op. I think because its so important, its gotten easier for me to stay on top of it than pre-op. it's ok if you don't get it perfect before surgery, at least you're making headway.
make it your priority when you get out of surgery though, and you'll work your way up in no time :)