If they are good neighbors, just mention it.
In our neighborhood, there is one house that seems to be the receiver for all that stuff due to the direction of the wind. We have had our garbage (actually recycling) blow over and I make a point of going to his yard and picking up all our trash. I have even had a couple neighbors that have seen me and helped out, and others that I have gone out to help, and we aren't an overly friendly neighborhood.
If you are less confrontational, maybe, when you know that they are home, or coming home and will see you, wait till then, and then clean it up...they may notice, and you can mention that the wind just grabs all the trash.