Wouldn't that mean "stay or remain on the balcony" here? http://italian.about.com/library/verb/blverb_stare.htm http://italian.about.com/library/verb/blverb_essere.htm http://dictionnaire.reverso.net/italien-anglais/essere http://dictionnaire.reverso.net/italien-anglais/stare http://context.reverso.net/traduction/anglais-italien/I+am+on+the+balcony
That is more like "at", "to" or "in" the balcony. It depends what you are talking about.
"su" is "on".
http://italian.about.com/library/fare/blfare114a.htm Simple prepositions http://italian.about.com/od/grammar/a/italian-prepositions.htm http://italian.about.com/library/fare/blfare153a.htm Prepositional articles http://context.reverso.net/traduction/anglais-italien/I+am+on+the+balcony
Because prepositions never translate well. I suppose we say "in the yard," just as we would say "in a field" because it's sort of an indefinite natural expanse. Though you'd say "on the field" when referring to a soccer or football field - maybe because it's an artificial space rather than natural, or because it has very obvious, definite dimensions?