Hi mercedes,
have a look at irishargentine.org. there is lots of info there to help you. i am aware that i have kelly ancestors that went from westmeath to argentina. visited argentina in 2004 and met up with walsh cousins who are descendents of the walsh faimly of ballinea, mullingar. you could try writing a letter to the westmeath examiner, dominick st. mullingar by email - they havve a website - giving the info you gave here. none of the other surnames ring a bell. if your family came from westmeath, they are likely to feature on passenger lists or in coughlans settlement lists. you could also check out the southern crosss newspaper in buenos aires, they were very helpful to me and also have a website.
cheers,