Are Africanized honey bees aggressive if you get near them, or only if you bother their nest?

Africanized honey bees are more aggressive, in general, than non-Africanized honey bees. In my experience, they are most dangerous when you get near their hives. Individual bees foraging on flowers, Africanized or not, shouldn’t pose a hazard as you are making observations, just approach with caution no matter what.