When I was mailing some things to my grandchildren, I wanted to put just "Gramma" for name in teh return address. The post office told me that if it doesn't have a first and last name, they would not accept it. So I am thinking that perhaps the same would hold true for mailing "to" addy. Worth asking before you go the trouble and expense of changing to a PO box.
Just my 2 cents worth.
Patti