as far as I know, most of the top 20 med schools will only give consideration to your ethnicity/race if you are:
1) African-American
2) Mexican-American
3) Mainland Puerto Rican
4) Native American
this is because they hope to give opportunity to those groups of people who have been most oppressed/discriminated against in this country. this doesn't mean that other groups have not experienced obstacles, but these 4 have been systematically mistreated by social and public institutions for hundreds of years and have only gained equal status in the last 50 years.
if you are hispanic but are not 2 or 3, they'll notice but it honestly won't help you out in the app process with the most selective schools. the top 20 or 30 ugrad colleges (who have the resources to evaluate apps on a case-by-case basis) also operate on the same system. if you are not one of these 4 groups but have experienced serious obstacles in your life (socio-economic or other disadvantage), by all means put it on your app, bc you will get the identical extra consideration that these 4 groups get.
another important point, for all you evil affirm action trolls, is that if you are a member of one of these 4 groups but you have led an extremely privileged life, you will not get the same level of extra consideration from adcoms. i know this isn't what they write on the web page, but this is pretty much how it works. hope this helps!