Drink driving is not a crime 'of moral turpitude':
http://www.gapsc.com/Professionalpractices/mor al_turpitude.pdf
Therefore, if your partner had applied for a visa, his conviction would be unlikely to prevent one being granted.
However, providing false information, in order to enter the USA, would sufficient reason for being refused entry
if the US authorities became aware of it.
Since the US immigration service have no direct access to any criminal records, except those of the USA and Canada, it's immaterial anyway.
Chris