I was at one time planning on studying here, but I did end up giving up many years ago so I might be a little lost.
What do you wish to legalize your degree for - to exercise your profession or for further studies?
For further studies I'm pretty sure it's just some trámites in the ministerio de educación (I don't know how complicated they are - I was trying to "revalidar" my high school studies, which I abandoned as they would not legalize them without my first taking 6 high school subjects...)
For exercising your profession, I don't know much about the process, I'm sorry I can't help you there, but be prepared for some paperwork, probably a bit of a waiting period, and from what I've heard, you will probably have to pay a good chunk of money (this is just from anecdotal evidence). (Oops, forgot to mention, that I imagine this is what you're trying to do, as you mention doing it through the UBA, which would be the place to go in this case)
Maybe this page will help:
http://www.me.gov.ar/spu/dngu/html/dngu_-_estudiantes_extranjeros.html
Looks like it depends on where you got your degrees from and if Argentina has a "convenio" with that country~!
