Definitely hawks will attack in front of you. At least, the juvenile Cooper's Hawk (I'll give you ONE guess what the common nickname is for this hawk is?) certainly tried to swoop down on mine! I was in the kitchen and just happened to look up and out the window in time to see some speckled wings swooping at the chickens. At first, I actually thought my barred rock was flying! I though, oh great, now I'm going to have to start clipping their wings so they don't fly out of my yard. A second later I realized it was the Cooper's Hawk attacking! He or she missed, and the Girls all ran for cover and froze.
Since then, its amazing how alert they are to the hawks...but I don't take any chances now. I only let then free range when myself and my dog can be watching them.