I think 'in' is more 'UK English' and 'on' is more used in the US. However 'on the street' can sometimes have a particular meaning: "The word on the street is that there is going to be an economic recession soon." (= We don't know for sure but that is the rumour; that is what 'people' are saying...)

Walk on the street and walk in the street. Are two of the phrases that are interchangeable in English. Meaning they basically mean the samething. It's just whichever sounds better to the user.