A quick follow-up... I also tried the various reg ex found here: https://stackoverflow.com/questions/5680050/po-box-regular-expression-validation
While they worked to prevent P.O. Boxes in various forms (box, Box, PO box, etc.) they also blocked standard addresses.
And I solved the issue of disallowing shipping for Alaska, Hawaii and non-US countries - just removed those options from the select lists.