Hi Gary,
As noted in the following KB, the "messages identified to be written in a disallowed language are deleted":
http://service1.symantec.com/SUPPORT/ent-gate.nsf/docid/2009062309004854
The same note is also mentioned on page 80 in SBG 8.0 Administration Guide.
Unfortunately, there is no way to bypass language detection, even for Local Good Senders, if you have chosen to block mail based on language detection feature.
Regards,
Adnan