Toilets are labeled with universal symbols or like these, so you really don't have to know the kanji for male and female. Various places might use odd symbols, but not in widely used public locations like train stations or hotels.
They might be useful for onsen, though. Those 2 kanji might be accompanied by ゆ which stands for hot water (spa, get it?), or they might have an additional symbol after the male/female symbol.
Japanese tend to be very accepting of mistakes in their language as used by foreigners. You don't want to give the impression you know TOO much upon opening your mouth for the first time. Just speak English slowly and avoid slang.
Perhaps learning how to ask for your drink in a meal to be served with the meal or afterward would be helpful. But this is all included in standard travelers' phrases. What do you plan to see and do? That might help us provide more accurate advice.