It sounds like I definitely do -- I live in Pennsylvania, and it's pretty cold for roughly half the year. But, obviously, I can't have anything that is too visibly a coop from the outside.
But in my situation, which is a 1/2 acre suburban yard within fences/walls, do I need to be able to lock two separate areas?
I am from PA originally and I am getting cold just thinking about winter back there. I think you need a coop for sure. I am not sure what you mean by locking two separate areas. Do you mean a coop and a run? If you want them safe, yes. If your run is very secure you can probably get away with letting your coop open, but come winter, you will have to make sure there isn't a cold draft blowing on your chickens. Ventilation should always be above them.
In your picture, I can't really make out what is behind your meters, but that is the area I would use. Under where the house sticks out on the right hand side. Here is how I would proceed. First I would install the hardware cloth on the area you plan to keep the chickens in, making sure it is nice and secure against predators. Then I would go ahead and put lattice over top of the hardware cloth for a decorative, garden look. Next, I would do my plantings and fountain. If anyone asked you could just say the lattice is going to be the support for the climbing plants. This way the hardware cloth will be less visible as well as the chickens. Once that was all in place, I would then go ahead and then build my coop.
I would probably build a lean to type coop off the back wall of your house under the part of the house that sticks out if that is possible. By attaching it to your house, it will look like a small storage or garden shed. Attaching the coop to a wall of the house will also give a little added insulation and protection to the chickens during the winter months. By building it under the house, it should keep that area dry and free from snow once you have the hardware cloth and lattice up. Remember snow and rain will go through your decking and get the area below wet. It would be nice to have a covered and protected outside area during the winter months.
If you prefer a free standing coop like the one in the picture I posted, you can go here for some directions on how to build a cute coop that wouldn't look much different than a dog house.
http://www.fresheggsdaily.com/2012/02/building-chicken-coop.html
Or you could get a dog house and convert it or some people use those children's playhouses and convert them into coops. I think there are several examples on here of that very thing. There are lots of ways you can do this, but do be sure and give them a coop.