Whatever booze u choose to purchase, remember u can get it in bottles larger than 1.75 litters. I bought a 2 litter bottle of Jack in Nassau and the empty bottle looks awesome on my mantel
Secondly, as far as sneaking alcohol on, I went on a spring break cruise last year and used Rum Runner flasks from the link below. I had no problem wrapping the flasks in my clothes and saved A TON of money!
http://www.rumrunnerflasks.com/