A Supermarket in California
Though we don't want to come out and say that the speaker and Allen Ginsberg are the exact same person (a speaker in a poem is always at least a little fictitious), the two are remarkably similar. Both are more than a little obsessed with Whitman, both write like him, both wonder about him quite a bit. No matter how much we may resist the idea, this poem is clearly autobiographical.
But does that mean that it's all true? Did Ginsberg really have an elaborate fantasy about wandering around a neon supermarket with Whitman? Was he really an incredibly lonely man, shopping for images? It's possible, but we'll never know the whole truth. That's why we refer not to Allen Ginsberg, but to "the speaker," when we talk about this poem.
And what a speaker he is—a little bit delusional (what, with his imaginary friend and all), a little bit lonely (why else would you have an imaginary friend?), and a little bit of a dreamer (he does seem to enjoy his jaunt through the aisles with Whitman). This is clearly a man who knows how to enjoy the pleasures a supermarket has to offer, but also knows that there's a great big world out there, and it's a little bit uglier and sadder than he'd like it to be.