Coyotes are common in Lake Havasu. They won't attack a dog on a leash being walked by a human, regardless of the dogs size. I've heard of rogue coyotes going over a wall and killing small breeds that were unattended, but have never known anyone who knew anyone that anything like that happened to.
When I lived there I had a German Shepard, and she would lay next to me on the front driveway when I sat out having my morning coffee. Many times a coyote would come strolling down the street and when it got too close she would take off after it. They would run like hell. They'll only attack larger dogs if they're in a pack. I've never seen or heard of that actually happening.
If a coyote sees you, they won't take their eyes off of you. They are very weary of humans. I would imagine if you managed to get one cornered, they would attack like any other wild animal. But if left on their own they won't get too close to humans, dog or no dog. There are very few stray cats in Lake Havasu, however.