I also have a balcony right off my living room and I let my 10lb Lucky out there because instead of railing it has a type of criss cross fence all around it. I also let Bella out there just as long as the curtains have been pulled back and I can see her. I know there is no way she can fall because there aren't any oppenings that her little head could fit through. Plus, my balcony faces the canyons and I live in southern cali, so the weather is never too hot out here.
Still, I get that you can never be too careful.