ad hoc -- common among academic writers, widely known among educated people, but not common in casual speech
per se -- reasonably common among everyone educated, but not that common in casual speech.
a priori -- only in legal and academic writing.
de facto -- common among educated people, widely used in newspapers and journals, but not that common in speech.
ergo -- pretentious, not used, but widely understood. often used to make fun of people who are acting too sophisticated.
et cetera -- understood and used by everyone in all registers of language. sometimes colloquially pronounced "egg cetera" especially among less educated people.
vice versa -- understood and used by everyone. first syllable is pronounced to rhyme with "nice" as though it were a native English word. Sometimes colloquially prnounced "vice-a versa."