Well, the howling behavior is the way the coyotes mark out their territory. They also leave physical markers like urine and feces but the howling is to tell other coyotes that this territory is held by a strong family and that other coyotes should keep away.
When they are hunting, they don't make any noise. If they howled while they were hunting they would never be able to surprise any prey! So the time you need to be careful is when it's quiet, oddly enough. And I do believe you should be careful.
Your coyote problem sounds scary to me. We have tons of coyotes here, but they don't bother people. In fact if it were not for the coyotes my whole house would disappear in a gigantic gopher hole... generally when we see them they are gainfully employed in digging up gophers.