Find the sentence and phrases that at first suggest that Leonard mead is the person living in this setting in 2053 AD in "The Pedestrian." Find the passage that reveals that there are other people living in this setting.

The first and second sentence of "The Pedestrian" reveal that Leonard Mead is the individual living in the setting described in the story and that the year is 2053 AD:

To enter out into that silence that was the city at eight o'clock of a misty evening in November, to put your feet upon that buckling concrete walk, to step over grassy seams and make your way, hands in pockets, through the silences, that was what Mr. Leonard Mead most dearly loved to do. He would stand upon the corner of an intersection and peer down long moonlit avenues of sidewalk in four directions, deciding which way to go, but it really made no difference; he was alone in this world of AD 2053 . . . .

Of course, it is only later that we find out that Mead isn't really alone. There are other people in his future world. However, Mead is alone in the sense that he is the only one out of his house, walking around. Everybody else is at home, watching television. Taking a walk alone outside is considered anti-social, deviant behavior.
We learn that Mead is not entirely alone in this sentence:

lights might click on and faces appear and an entire street be startled by the passing of a lone figure, himself, in the early November evening . . .

This reveals that people really live in the ghostly houses with the firefly-like lights on behind curtains.
Later, Mead will also encounter the police, but it will be through an empty, automated car that stops him and takes him off to the psychiatric hospital. In the story, Bradbury critiques an increasingly technological world in which old-fashioned, simple activities like taking a walk are no longer socially acceptable.