Before reading this section, you've got to listen to Brooks reading the poem herself, which you can do at Poets.org.
Is it different from how you imagined it? We could sit and listen to her say, "Seven at the Golden Shovel" all day long. Her voice produces deep vibrations like a low saxophone. It may be obvious to say, but there's no avoiding it: "We Real Cool" reads like the lyrics of a jazz tune. Brooks has even provided musical instructions to how it should be read, with the low, quiet, uncertain "We."
When you listen to the recording, the most obvious musical element is syncopation, or the uneven distribution of the rhythm. That's why it's so hard to talk about meter with this poem. A meter implies a regular rhythm, and, on the page, "We Real Cool" seems pretty regular, with three beats followed by a pause. But the arrangement of the words lends itself to wild swings of improvisation.
Listen to how Brooks pronounces "strike straight," by laying into the first word and backing off the second slightly. She literally "strikes" at the first word like a fist coming down on a piano. If you were reading the poem, you might be inclined to give both words the same amount of emphasis, but Brooks lengthens the first beat just a tad: that's syncopation. Also, when she says, "Thin gin," it sounds like a bunch of people shouting and clanking their glasses so hard they're about the fall off their bar stools: "Thiinnnnn Ginnnn!"
To some readers, "We real cool," may sound like an ironic whisper saying, "No, you're not. Stay in school!" But if you read it aloud like Brooks does, the irresistible pull of the rhythm can also lead us to sympathize with and relate to the boys.