Does the size of a 町 determine if it is pronounced machi or chou?


北谷町 and 下町 The first one is pronounced Chatanchou and the second is
Shitamachi. The second term is within an area of the the first one. Is a machi
smaller than a chou? In the past was the term ノ・の used in between the kanji to
indicate a machi, for example shita no machi?




In the east of Japan, Machi is used more often.  
In the west, Cho is used more often.  
Google “まち ちょう” and you will find a good picture.




If you study kanji more, you'll realize that _both_ readings are acceptable
depending on the circumstances. Learning what reading is correct in each
situation is something that you will have to practice a lot before you get the
feel for it.

In general, more populated areas tended to be read まち, and less populated
areas tended to be read ちょう, but exceptions were _very_ common. Additionally,
as @Yosh as pointed out in the comments, size of the region doesn't
necessarily affect the reading either.

For the purpose of addresses, in my experience a まちand a ちょうare mutually
exclusive since they mean the same thing. So no, a まちcannot be in a ちょう, and
the opposite is also true.

