Product review (5 stars): Very good sign - clear message
I had to get this one because my previous sign was magnetic and "turning" thus non-reliable.  Plus it was taken by the toddler and thrown under the dishwasher.

As for placement choice, I did not want to put it on the dishwasher's face for two reasons:

1 - it would be at your waist level making it hard to read; and
2 - the same toddler could easily reach and switch it, just for fun

Standing in front of my sink/dishwasher area, I looked at the focet and realized!!  (I have sink and dishwasher as a island)  I can glue it to the side of the counter edge above the sink.  It is within immediate reach to the person who is doing the dishes, and it is on a good level for your eyes to see, AND it is far away for a toddler to rich to it.

I am sure you can do the same even if your sink is by the window - just stick it to the backsplash behind the sink.