I've yet to deal with an organization that has a GPG/PGP key for encrypting email to the organization. I don't think there's anything wrong with asking if they have one for encrypted email use, and so I think it's fine if you go ahead and do so, but I also don't expect that they have one.
What is more common is for the email MTA to support SMTP over TLS encrypted transfers. This can be verified using 'swaks' by testing each of the company's email servers listed in DNS one by one.
Finding the mail servers that cover a domain, for instance "nonsense.com":
$dig nonsense.com mx +short
$swaks --ehlo testing.example.com --server nullmx.nonsense.com --tls -q TLS
=== Trying nullmx.nonsense.com:25...
=== Connected to nullmx.nonsense.com.
220 mx ESMTP
*** Host did not advertise STARTTLS
=== Connection closed with remote host.
If the company email MTAs all DO support SMTPS, then perhaps that will be good enough. Even if the company did support GPG, there are certain things such as the Subject for the email which don't get encrypted, so SMTPS is important for those reasons anyway.