Pat Mora's poem Legal Alien is about the life of a Mexican-American woman who, as her heritage descriptor shows, is "literally" half of one thing and half of another according to the standards of society; not to her own.
While the narrator feels quite complete as an individual, she does admit that having both heritages may look complex. However, she shares that shifting from one heritage to another does not affect her at all; she is able to be just as complete as a citizen whether she is speaking Spanish or English.
Yet, within the Mexican and the American "sides" that she sees everyday, there is always a conflict. Is she Hispanic enough? Is she American enough? How much of each will she let show in her daily behaviors? This dichotomy is what leads to the title "Legal Alien": No matter how normal Mora's life is, and no matter that she is a woman born in the U.S. territory (she is from El Paso, Texas), she will always be seen as a half-breed life form.
able to sit in a paneled office
drafting memos in smooth English,
able to order in fluent Spanish
at a Mexican restaurant,
American but hyphenated,
viewed by Anglos as perhaps exotic,
perhaps inferior, definitely different
As a "hyphenated" citizen, her nature makes her still an alien regardless of the fact that she has lived as a regular American citizen her entire life.
Another issue in her "hyphenated" existence is the latin-to-latin bias. The fact that she speaks English, blends in with all citizens and tries not to stand out as a result of her culture makes her an alien among her own people! Perhaps in her daily life she is expected to be "more Mexican" or act in specific ways. Since she chides away from it, she is put in a situation where she just cannot win: she will never be white enough, nor brown enough, for the likes of the people who surround her.