[Sileni]

I have no experience with modern variants of Latin, but wouldn't that be akin to trying to read Portugese when you know Spanish? You might get the general gist, but you wouldn't really get the full underlying meaning. You'd certainly miss more complex ideas like idioms.

I'd imagine it would depend on your goal. Do you want to be able to work your way through a text, or do you want to be able to appreciate poetry in the language? I'd say it might work for the former, it almost certainly wouldn't for the latter.