I forgot to report it, but the translations of "hezký" vary between "nice", "pretty" and "cute", with several sentences only accepting one of the options. While I get some of them ("Have a cute weekend" might be a strange thing to say), sentences like this one are ambiguous enough, that I think all three should get accepted. Or is there something I'm missing here?
copy of my previous explanation
The problem here is English and how Duo handles the courses. NICE when you speak about people in English does not refer to their external beauty but rather internal. BUT if you say 'nice' about a car in english, it refers to what it looks like and can be translated as 'hezky'. So the word 'hezky/hezka' has both hints but in this case only one can be used.
-é is a female form, male animate form in that case would be -í: "jsme mladí a hezcí"
-é could also be male inanimate form, not exactly in that case (given the context), but you could say for example "the castles are big" ("ty hrady jsou velké") or "the machines are expensive" ("ty stroje jsou drahé").
Ok. Does this sentence not at least connote that the group being referred to consists of females? It seems like if I just translated the sentence to an English version identifying people in general, it would not be COMPLETELY accurate since the feminine gender was implied via the "é". I understand why adding a noun such as "girls" or "women" would not accurately connect to any word in the original Czech sentence, but with that "-é" ending, wouldn't it be MOST accurate to translate the sentence to the accepted answer, while also identifying (via parentheses, a checkbox, whatever indicator you wish to use) that the people the sentence refers to are all female? (Implying that other gender modifications would be used to describe correspondingly differently mixed groups of genders?)