My dogs hate coyotes, but they don't try to engage them either. The older dog we gave to my daughter had spent some time around them because he used to get out and stay in the desert for 24-36 hours. He hates coyotes as well, but avoids them if possible. When the other two were pups, Dan would stand guard over them while they retreated to the back porch. I think Dan somehow got the idea across that coyotes were dangerous and not to be tackled unless cornered. At 50 lbs, the Border Collie is about the size of the coyotes around here, while the Australian Shepherd is larger - but 2 against 6 or 10 wouldn't work out so well either.
Mostly, I'll just see 2-3 moving along the wash. As long as they are just passing thru, neither horse gets too upset. The dogs will bark, but won't give chase.