"The answer is yes... and no. The simple rule is that you can photograph nearly all public places and spaces. You can also photograph people in public as long as it falls under editorial content. What is editorial content in regards to photographing people? How does it differe from photographing people in another manner?
Editorial content tells a story, shows an environment, records an event. The subject matter is the image as a while - any people in the photograph are a component of the story. They are not the story itself. This is different from portraiture, you are photograpghing a person as the subject matter and the photograph is meant to capture her likeness."
Knowing when to take pictures of people or where? Whether of not your on military or government property, you can't but in a crowded area or a parade you can.