Question

many of the people who have come to mexico city have ended up living in areas

Answer 1

Many of the people who have come to Mexico City have ended up living in "surrounding" areas, since life in the city itself is very fast paced and dense, meaning that many people wish to enjoy the benefits of the city without being there directly. 

Answer 2

Many of the people who have come to Mexico City have ended up living in areas _____.

 with no sewage or running water