It was written in English. I read it around 2013-2014 in British Columbia, Canada when I was in middle school.
It could have been a short series, or one book.
The protagonists are young adults, and so the book was probably for young adults.
The setting is a post-apocalyptic/heavily resource-drained world, with the narrative taking place in the United States; I don't believe the author explains why the world has gone downhill. The government only retain a loose control over some places.
(At possibly the beginning.) The group of several protagonists join a walled community, they regret it, and now they plan to flee through the sewers. They have an argument about leaving behind someone who is ill and would not be able to flee with them. When that community finds out they've fled, they quickly assemble a group to chase after them into the forest. A member of the search group is described briefly as "gung-ho" I think it was the first time I ever saw that word. The chased protagonists are then split up into 2 groups, who manage to escape. They had planned to meet at Salt Lake City in case of this, I believe.
In a later scene with one group of three protagonists (2 male, 1 female), one of the male characters uses up a bunch of food, including a bird he's killed to have a Thanksgiving celebration in their makeshift cave shelter. The female is happy about the celebration, but also questions whether they could afford it. They later travel down the road.
The three are captured by a gang of bikers/bandits they take them to a zoo where they have taken up residence. The gang leader is like a king. Most of the animals have been eaten by the gang already. They plan to feed the 2 males to the alligators while the female becomes a slave to the gang's leader. The other slaves take her to have make-up and different clothes put on while she cries. Another slave-girl gives her a tip "When he enters you, don't cry, he hates that".
In a different scene, the other group of two protagonists (1 male, 1 female) are walking through a city (Salt Lake City maybe) and a soldier described as a 'Peacekeeper' asks them why they aren't in school. The boy is worried about them not having a passport. He lies to the guard something like: "Well, you see, we're young lovers who have recently gotten engaged". The Peacekeeper feels sympathy for them and lets them go.