It absolutely matters
While it may be true that Latino pop stars and actors have done much to enhance the image of Latin men as objects to be desired, the fact remains that there is a certain stigma attached to being Mexican (especially in the northeast)--the other Latin cultures do not seem to suffer as much from this. To wit: Have you ever noticed how many Mexican jokes there are? Any Puerto Rican/Colombian/ etc. jokes that are out there are simply Mexican jokes that have replaced the word "Mexican" with some other ethnicity. You are plagued with the term "wetback" and the stereotype of being on welfare, the ability to fit 10+ people into a compact car, and as having the education of a 10-year old. Indeed, it is difficult to be considered beautiful outside of your race when even your own peers don't consider you as such (e.g., look at the soaps on the spanish channel that are set in Mexico; you'd swear some of the men jumped out of an Abercrombie catalog).
Of course, there are some people from Mexico who have more European looks: these are the ones for whom race does not matter. If you have strong indigenous features, however, you will struggle to attract women from outside of your race. Do not be mislead, many of the hispanic/white couples that are found in various statistics on interracial relationships involve an hispanic person that considers himself or herself white. The only succesful interracial couples that I have seen involving a Mexican male and a "classy" white woman are those in which the male is educated and has little to no connection with his culture (at least, that's what I've seen here in NY).
On the other hand, if you like skanks and hors, then your race shouldn't matter that much.
