Board Thread:General Discussion/@comment-30088034-20170222171154/@comment-27701762-20170222212921

Presumably. At least for the most part. Some monsters do recognize you as human (e.g. Temmie, Tsundereplane), but for the most part monsters in the overworld do not realize you are human, and in fact there is a specific explanation that monsters use magic to express themselves to one another (that is, the attacks being used in battle). Since the explanation is there and so few monsters actually acknowledge that you are human, it's more than likely they regard Frisk as a fellow monster.