Of all the lines written by Shakespeare, this is possibly the single most misunderstood by a 21st century audience.
While it might be a romantic notion for a lovesick teenager to look out her window— not a balcony, by the way— and wonder where her beloved might be, that’s all it is. That is not what is happening in this scene.
In early modern English, “wherefore” meant “why”.
Juliet is not asking where Romeo is. She is asking why, of all the families in Italy, did her new boyfriend have to belong to the family with which hers had been feuding? Why did he have to carry a name that would be an immovable obstacle to them both?
She goes on to insist “that which we call a rose by any other name would be as sweet”— in other words, it’s not the name that makes someone what they are. If Romeo were to change his identity, he would still be the same person. What his name is should not matter — what sort of person he is, and the fact that she loves him, is what should determine their compatibility.
That’s why when you’re waiting for a friend or looking for your dog, it’s incorrect to ask “Wherefore art thou, Buddy?”
It may sound cute, but it will make your Shakespeare-loving friends cringe, at least on the inside.