People of mixed european and african ancestry, part of the common class of latin american society?

Yes. Especially because most mulattoes were the descendants of African slaves and their European masters, born out of marriage. Very few of them were actually recognized by their parents, inheriting their education and fortune.

An unfortunate result of this colonial Caste System is that nowadays, most Latin Americans of African ancestry are disproportionately "economically challenged" than the rest of the population.