This is more of a setting than a plot-- that comes with making characters that are interesting and keep the readers attention.

Here's a few observations about the idea that might promote a plot...

It sounds like you're suggesting hard labor. Anything that has prisoners in a position where the guards have extreme discretion in how they treat them would have to involve the kind of crimes that make a family member turn their backs on the incarcerated prisoner. Signs of obvious abuse would lead to investigations and civil litigation-- the women in your story would have to be forgotten for a reason. Capital crimes.

As a suggestion, how about a central character, a woman, that killed her policeman husband? Perhaps he was a closet sadist and he let his coworkers have their way with her at a holiday party, and she shot him when she finally got free.

As for a plot, a prison break would be one way to give the situation a story and a direction.

Or, the men could release prisoners just to practice recapturing them and for the thrill of the hunt, and our main character fights to avoid recapture and a brutal raping.

If you wanted to go highbrow and add a little something for everyone, a romance while on the lam with a helpful bystander might be a fun twist. Seeing our main character(s) regret their former wickedness while coping with corrections officers trying to capture them.

As for locale, if you wanted to avoid using South America, there's Florida or Louisiana, both have large swamp lands that make flight very sticky. I can suggest some movies that coulkd give perspective on flight and travle in that area.