I don't think being descended from Conquistadors is admirable. History is what it is, but not something to always be proud of.
I do think its admirable. They were part of an important time in not only American history, but world history as well.
Yes, at first the Spanish did mistreat the Natives, but following Pope's' Rebellion from 1680-90, it dawned a new age of the assimilation of the cultures. From then on, there was a mutual respect of both races, and they were encouraged to mix the blood.
And also, not all Conquistadors were all that bad. Cabeza de Vaca, who made friends with many Indians on his trek through Texas back to Mexico City, comes to mind.