[fjtorres]

I can't speak to the french issues directly as I haven't used my french more than a handful of times since my college days (and lately I'm wishing I'd taken russian or japanese instead) but I think I can say something about the mental translation mechanism.

And that is: don't.
Not if you can help it. Not if you aspire to eventual fluency.
I live in a bilingual environment and I've seen it on both sides of the divide; it is the most *natural* thing to do, to compose a thought in the familiar language, translae in internally, and then vocalize it. Or, in reading, to translate the words and rebuild the sentence in the language of comfort.

It works, mind you. It'll see you through the discomfort of the situation. In the short term. And it is better than no communication. But if the intent is to achieve fluency it is best to muddle through the haze of partial comprehension, relying on dictionaries and thesauri when you hit a roadblock, until you build up enough familiarity to directy go from word to concept or vice-versa. To start thinking in the alternate language. You might have to return to the book at a future time for further insight but everything I've seen and heard tells me that the road to fluency is faster through immersion than on-the-fly translation.
FWIW.