Both are grammatically correct but the first one can have two meanings.Originally Posted by dcomest
walk the streets means to walk from one street to another, especially when one is looking for a job (same as pounding the pavement).
If you say, young teenage girls in Vancouver are walking the streets late at night, it means they are soliciting as prostitutes.
Myself I would use #2 or else you can say "he was walking down the street.."
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