Marcelo in the Real World is, as the title suggests, all about someone who has to leave his own comfortable internal world and interact with the world at large. Marcelo's sheltered life at home and at Paterson has allowed him to cultivate his own strange verbal tics, like referring to himself in the third person. As he becomes more a part of the real world, we see him learning to speak differently: he starts to use personal pronouns a little more often, and he starts to use slang. For example, he mimics Jasmine when he says "hunky-dory," and he uses the word "fucking" instead of "sexual intercourse" to differentiate what Wendell wants to do to Jasmine from the clinical concept of sex he's had up to that point.
We know how much Marcelo has changed throughout the course of the book by the fact that on the last page, he consistently refers to himself as "I" rather than "Marcelo." He even uses a metaphor in the correct way: when he tells Jasmine he's going to Vermont with her, she says, "You need to make sure you come for the right reason," (31.79), and he says, "It has to be the right note" (31.80). Now that's some understanding of context.
There's an old adage that writing teachers love to toss out: "show, don't tell." If you've never heard it before, it means that a story is much more effective when, for example, instead of saying, "Jasmine's family is poor," you let us see the faded lawn ornaments in her dad's yard. Likewise when Marcelo says, matter-of-factly, "Robert Steely lives in a neighborhood where the houses are closer together than where I live" (20.23).
Also, the line, "Cody, go get your fiddle while she's peeing" (23.41), as spoken by Jasmine's neighbor Samuel Shackleton, is one of the best examples ever of showing rather than telling. There's no need to tell the readers the guy's a hillbilly when you give him a line like that.