I believe you will have no roof over your balcony and the public floor above you can look directly down onto your balcony, depending on what's above you. It's offset such that anyone looking over a railing can look right down on you. I'm not looking at a deck plan right now, so I'm not sure if what's above you is an oven rail or an enclosed area. If it's part of the enclosed area, it might not be too bad. But again, there's no overhang forming any kind of roof over you.
Warning, this is ALL assuming the deck stacking design is like Coral and Star, which I believe it is. I booked for August on Sapphire and researched this well as I was on Star and had no roof and no privacy on the balcony.
The balconies on the Diamond are set up just like those on the Grand / Golden / Star. Aloha deck balconies are completely covered as are those on Baja. Caribe deck's balconies are half covered and half open and Dolphin deck balconies are completely exposed. Emerald deck balconies are completely covered. This should be a nice location for you. Have a great cruise!
I seriously could have sworn when I was on Star that I looked up and could see that Aloha was exposed (or some, but maybe not all are depending on location). I remember this because it wasn't long after a cruise on the Coral where friends on Aloha got their cabin changed for this reason. And then I looked above me on Star and noticed it was in a similar arrangement. I could still be wrong, of course. I'll have to look for a picture.
Yep, LK is right. They managed to cover Aloha, unlike on the Coral/Island and Grand/Golden/Star. I'm booked for Sapphire in August and avoided Aloha because I thought it was uncovered. We booked Baja, but Princess later offered us a room on Caribe. Same room size, bigger balcony, so we didn't mind the lower deck.