This week in Minnesota a young boy miraculously survived a fall from the balcony of his 11th floor apartment. He had squeezed between the bars on his balcony railing which were 5 1/2" apart. The modern building code specifies that the space between railing bars should not be larger than 4". Every year there are scores of children that die or are injured from falls from balconies or open windows. Please be sure to address these issues so that this does not happen to your child.
There are many safety products that can be installed to keep your curious toddler safe at balconies and railings. There are several styles of barriers that can be attached to existing railings to cover up the wide openings and also prevent climbing by your child. Here is a link .
There are also barriers that can be attached to the inside of windows to prevent children from falling out. The screening in windows is not strong enough to prevent a child from getting through it. They are called Window Guards and come in different sizes to fit your opening.
Here is a link to another KidSafe article on Outdoor Balcony Safety.