In the last vignette Mango Says Goodbye Sometimes, Esperanza states,
"They will not know I have gone away to come back. For the ones I left behind. For the ones who cannot out.(110)"From this quote I can draw many inferences. But one that makes much sense would be saying that Esperanza will most likely go away, get her life together, and maybe get an education, so she can come back to Mango Street and help the people there. Some of the people that live there, have been there forever and don't know how to get out because they're so attached. But Esperanza wants to change that, she wants to help them know that there is more to life out in the world.
Going back to the independence of women, earlier in the book there was a vignette named Rafaela, and it tells the story of how Rafael's husband wouldn't let her out of the house because she was too beautiful.
"Rafaela leans out the window and leans on her elbow and dreams...(79)"I believe that Esperanza is going back to Mango Street to help the people like Rafaela, who can't escape out because either their husband's are controlling them or society is closing them in.
That also leads me to the conclusion that Cisnero's character Esperanza might have written this book to help the women of Mango Street; or women all around the world like them. To show them that they can be independent and it's okay to achieve their dreams and bend the rules of society a bit. It is okay for women to fight back and stand up for themselves. And they should do so.