Flavia, you may have used the wrong demonstrator in your "this people don't..." If you so desired, you might have written and implied, "these people don't..." or "this kind of people don't..."
Silvia Mattos, on your "You never can trust..." You might have thought of putting "never" in mid-position. Like this: "You can never trust..." More often than not, we place never after modal auxiliary verbs. Such as can. Or could, at least.
At my own risk and loss, you might have thought of lynching me. Not only do I sometimes fail to greet my neighbors, but also I won't hold the elevator door open for them. All on a "First one in, first one up or down" basis. To add injury to insult, I have a small 4 door sedan equipped with triple yet powerful air horns to warn other drivers that they've just cut me off. To make things more miserable, you can never know what the guy on the next corner will do. Will he pull a gun, a knife, on you as you walk by him? Why do newspapers sport so many ominous headlines then? Little nowadays does big city living have to offer in terms of personal safety.