Translation:Do you want to live alone or with friends?
朋友 in Chinese has a similar nature to uncountable nouns in English. The word does not explicitly refer to "one" or "two" or more friends, as it can both describe a single friend (e.g. 我的朋友) or a group of friends (他們是我的朋友). So the original sentence can be understood both ways.
However, to make communication clearer, it is good to say 朋友们 in the above sentence if you want to say "friends", and better to say 一個朋友 if you want to make it very clear that it is only one friend.
I read somewhere that 们 can be added to "animate" nouns to make them plural. So, could 们 be used to pluralize ANY noun referring to a person? For example, could I say 医生们 or 老师们 to refer specifically to multiple doctors or teachers? Or is 们 used only with a more limited group of nouns?