you could create a second set of data and use that for reporting porposes, you could create it in Column F to I as follows
Col F =IF(ISNUMBER(FIND("PO BOX",$A1)),"HOMELESS",A1)
Col G =IF(ISNUMBER(FIND("PO BOX",$A1)),"San Francisco",B1)
Col H =IF(ISNUMBER(FIND("PO BOX",$A1)),"CA",C1)
Col I =IF(ISNUMBER(FIND("PO BOX",$A1)),"94109-0000",D1)