This means some zones will have more than one fast travel map, as some of the later areas like Venice Beach are actually quite big. With fast travel, you can quickly move to any previously visited safehouse that also has a fast travel map inside of it. Some, but not all, safe zones have fast travel maps. You kind of just stumble upon it eventually. Below you can see a screenshot of one as an example, since the game never really makes this obvious. Once you unlock your first few zones in the main story, you can fast travel easily by approaching any of the red Los Angeles maps you'll see inside safehouses. Though the game never quite telegraphs how to fast travel, we've already beaten it and can help you easily right here.
Knowing how to fast travel in Dead Island 2 can shed hours off your total playtime, and though you might like a nice long game to jump into, you'd be better off spending that time by tackling the game's many missions and chasing loot rather than simply back-tracking.