Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
Third Person (Omniscient)
The narrator of Tortilla Flat is outside of the action but has access to pretty much every character's secret thoughts. Every now and then, the narrator will call him- or herself "I," with statements like: "In the year of which I speak [...]"—but we don't have any real information about who that mysterious "I" is. He or she isn't actually a character in the story.
This use of the first person might remind us of the oral tradition of the King Arthur legends, where a speaker tells a memorized story around a fire. Steinbeck did model aspects of Tortilla Flat on these legends, after all. We think Steinbeck probably chose a narrator like this primarily so that he could show the entire community, in and out. What do you think?