emk wrote:Even just native English → French transparency is huge. It's a standing joke in our household that you can just take any big English or French word, and change the pronunciation to get the other language.
This is only ever more advanced vocabulary transparency and limited by the problem of a huge number of false friends. English in daily use language is almost entirely a Germanic language. Nearly all its common words are of that origin.
And as s_allard pointed to there is the rather noteworthy grammatical (and syntactical) difference, plus structures that simply don't exist in English. The basic structure of French is nothing like English, there are just some similarities sometimes which is misleading. In fact this is perhaps the initial hurdle in both directions. A friend of mine whose first language is French (though one parent is Dutch) returned to NL after schooling in France and really struggled to learn Dutch. When they started with English he also struggled with that, and it was only when he reached advanced vocabulary that the overlap started. As such he uses those words more and tends to sound 'educated' in English, but stumbles more over what would be seen as 'simpler' English.
There's a lot of to-and-fro in this thread and I wouldn't say that I completely reject every last bit of what s_allard is putting forward, except for the time factors and limits on vocabulary. Since it is possible to be somewhat functional with a vocabulary of a limited size. Even though this will be full of holes and handicap you at times. Doing a lot with a little when core grammar is well understood has its place. I still subscribe to the approach of: a little grammar well understood and as many words as possible over time.
The main subject at the core of this thread is time. As in: what can you realistically build in x amount of time? I say that a month won't give you a great deal and even three months is only scratching the surface; even if a person believes they are paring down everything and planning for efficiency. It's not a realistic prospect. You'll have something, but it won't be much.
The questions around getting a leg-up from other langages are being suggested in a disingenuous manner. If I 'start' Spanish today, but actually I've done it before several times in the past and also know Italian, I am not really performing what the question implies. As leosmith remarked, try it with some difficult and perhaps unrelated languages and see this masterplan fail miserably. Additionally, other aberrant and anomalous exceptions keep being offered to make the peg fit the hole. That someone COULD perform these feats if they studied 10 hours a day. That they COULD learn vast numbers of words in small amounts of time if they employ this or that exaggerated stratagem.