Anecdotally I only knew two Trump voters in the Bay Area. One is Chinese and the other Indian. Polling was not great in the last election, maybe because pollsters can mainly call people with landlines [1] which excludes large pools of people.
Exit polls are different from opinion polls. The surveying techniques are entirely different, and in general exit polls are considered far more accurate than opinion polls -- because you're polling on a concrete question ("who did you vote for a few minutes ago") rather than a less concrete one ("who are you more likely to vote for").
Considering how many people were shamed for voting for trump I’m not entirely sure how accurate those exit polls were as most of them predicted a landslide for HRC before the count started.
Exit polls are different from opinion polls. The surveying techniques are entirely different, and in general exit polls are considered far more accurate than opinion polls -- because you're polling on a concrete question ("who did you vote for a few minutes ago") rather than a less concrete one ("who are you more likely to vote for").