What we know about Geraldo is obviously very limited. We are told that he likes to dance, he is good looking and young. He was wearing "green pants" and a "Saturday shirt" when he was dancing with Marin. He works in a restaurant. He is also obviously an illegal economic migrant, working illegaly in the United States to send back money home to his family. Apart from that we know nothing more.
Yet this is precisely the point that Cisneros wants to make. This vignette reveals to us the harsh existence of such migrants like Geraldo. They live their lives in fear of being deported and are forced to work in low paying jobs, living in terrible conditions, such as the "sleeping rooms" we are told he probably rented. As "just another brazer," he "always looked ashamed" of being illegal and having no status. He was not able to tell Marin any more information about himself, not even his last name, because of the way that fear forces him to live a life of secrecy. Thus the very limited description we have of Geraldo's character reinforces the central theme of this powerful fragment.