What does this notice mean? That gambling is prohibited and that drinking is prohibited too? That it is prohibited to gamble and drink together, at the same time? (In which case the plural verb “are” might not have been used.) That gambling and drinking (together or separately) are prohibited in this particular place? (If so, from where to where?)
One can just gamble about all the possible meanings of this unsigned notice.
Addendum (1st September 2010)