walk on the street - saying that you're walking on the street as opposed to on the sidewalk or on the grass. Walk in the street. = You are literally (actually) walking in the area used by automobiles. Usually americans say this referring to the danger involved. Mothers will often warn their children: Don't play in the street! walk along the street - walking down the street They're all correct depending on what you're trying to say.

In = inside. I am in school. Along would be next to something (you walk along a path. You walk next to it) So you are walinking on the streets. Think of : on top of.

Walk along the street is the best one