Good morning and thank you for your question.  It is definitely that time of year as I am also seeing grubs in my veggie beds. I've just been tossing them in the lawns for the birds to enjoy.   The grubs were likely there munching on the roots of grasses and weeds present in your beds as that is their preferred food source. 3-4 per square foot seems high, but really control is not warranted unless you are seeing closer to twice that.  Turning the soil and just hand picking can be a safe way to keep numbers low.  I wish you all the best with your gardens.  

Thanks.