Although the events taking place here are absolutely fictional, the place known as Boyle Heights is absolutely real. It has a wikipedia page and everything. For the sake of the fiction, areas can be described in an extreme way. But people do live and work there and have pride in their community.
Another absolutely real thing in "The Beast of Boyle Heights" is Hollenbeck Park. The park has a long and sometimes sordid history. It is meant to be a beautiful place and the parks department does do the best they can to make it nice for visitors. The lake does tend to be badly polluted though. People aren't always considerate of where they dump garbage.
Abuela's Panaderia is not real. There are numerous panaderias in Boyle Heights and Los Angeles, but the place Maria worked does not exist. Eliza imagines it looks like this though.
The tent city at the edge of Hollenbeck park is not real. There are numerous homeless people in Los Angeles. California has a lot of homeless and the reasons are fairly simple. Colder states often deal with homeless populations by shipping them one way to another state. It is cruel in some ways, but practical in the most limited sense -- people living outside are far less likely to freeze to death in California. The tent city concept isn't foreign to California either. Little communities of homeless do crop up in places where they aren't chased away. There is safety in numbers
James Caffrey is fictional and so is his little empire. It's hard to image one man running as much of a community as Caffrey does. But it makes for a great story.