Speaking as an American teenager:
Girls will say "I went out with my
girlfriends" (meaning friends who are girls), "I went out with my
boyfriend" (meaning a boy whom they are dating), or, at least with teenagers, "I went out with my
guy friend" (referring to a boy who is your friend and only your friend). I've never heard girls says "boyfriends", plural, as that would imply she was dating several men at once!
Boys will say, "I went out with my girlfriend" (meaning a girl whom they are dating), "I went out with my buddy" ("buddy" is used for friends who are boys. "Buddy" is rarely used for girls), or "I went out with my friend" (which can be used for both boys and girls).