I was just having a conversation with my wife about a similar topic, how many people don't have enough education to understand design. I'm not suggesting that anyone in particular is lacking in knowledge of design, but I wonder how many people have actual education in the concepts of design and how many just picked up bits here and there (like me). I was never taught much about art of any kind until I specificaly sought it out, so I always feel behind when it comes to conversations about design elements. I have learned quite a bit, and have had the opportunity to study with people who have a great understanding, but it takes time to internalize these concepts.
When I'm out with the camera looking for interesting things to photograph, I don't go through a list of rules, but rather rely on what I have been able to internalize to the point of it becoming automatic. The more I photograph, the more of these concepts begin to shift to automatic mode.
Interestingly (to me anyway) I find that I can openly discuss design concepts with artists who work in other media, but have difficulty talking about them with photographers. Again, I'm not trying to imply that photographers don't have the artistic background that other artists do, but I do find that photographers tend to talk more about subject matter and technical aspects that other types of artists.