A friend asked this question on instagram, while instagramming her slushie. We're from an equatorial country, and that made me think - we've more or less taken ice for granted, whether it's used in our desserts (shaved ice, etc) or for chilling drinks.
Did we have "ice" pre-Industrial Revolution, then?
Mountains still have snow/ice and it still will occasionally hail even in the tropics.
Even in the equator you have hail storms now and again, and you can see it melt, so they would be able to figure ice out even without a traveler coming with stories from mountains or colder weather.