In Harper Lee's To Kill A Mockingbird, is Scout the one who states the following?A Negro would not pass the Radley Place at night, he would cut...

Yes, but this is not a direct quote from five-year-old Scout, it is Scout in her adult voice as narrator.

The passage you quote comes from Chapter One.  Scout opens the book narrating in the first person about events that happened over several years in her childhood, beginning when she was "almost six."  She is looking back on these events from a distance of time.  In Chapter One, she gives a lot of background about her family history and the conditions in her town and immediate neighborhood at the time.  This is information that was known to the child Scout, though she would not have delivered it in the confident and well-organized narrative voice that the adult Scout uses as she tells the story. 

The passage about the Radleys' yard, which begins, "A Negro would not pass ..." is information that was generally known in the neighborhood during the years Scout was five and six.  Scout-the-narrator is supplying this background information so that the reader can be up to speed on what the child Scout, and every other child in her neighborhood, knew about the Radley Place.