This is the hometown and the main setting in the novel. The main character and his love interest reside in Jefferson Park (along with everyone else in the novel). It's described as a "massive subdivision, because that's what Florida does with land" (Prologue 2). It is not a remarkable town and this is important because it's the reason why Margo (the main character's love interest) decides to leave in the first place. 

After some digging, I found out that the fictious town of Jefferson Park might actually allude to the very real town of Baldwin Park in Orlando, "We drove down Jefferson Drive to Jerfferson Court and then turned onto out road, Jefferson Way." I marked the location as Baldwin Park in the map.

Basically, Jefferson Park can be literally any small suburban town, it really doesn't matter, what matters is how Quentin (the main character) and Margo feel about it; Quentin doesn't seem to mind it too much, but Margo detests her small hometown and the people, which can be seen with this quote "The people are the place that is the people."