I would not keep them in water. I would wrap the entire plant in moist paper towel or if you are in a hotel you can wrap them with moist toilet paper. In water I would be afraid of rot. I have never been able to root a leaf from this plant so it is probably not of any use.
When you get home you will have to remove the bottom leaves to plant anyway.
I will give you some of my background. I had a job that took me through every state in the US and Puerto Rico. In some of the warm or tropical cities I would be there for a week and coming out of the hotel the landscapers would pull out plants, break off plants and throw them into their barrels for disposal. I was constantly snatching them out running back to my room wrapping a succulent, cactus in toilet paper or the USA Today moist paper. I would not return home for a week and nothing died being wrapped in moist paper.
