I think you can manage to learn quite a lot of Chinese till then if you focus on speaking rather than writing abilities. It takes rather long to learn Chinese characters, particularly at the beginning, but you could acquire quite a large speaking/listening vocabulary if you accept that you'll know some words in Pinyin only.
I find Chinese vocabulary rather easy to learn because many words are only 1 or 2 syllables. Of course they're completely foreign-sounding syllables, you can't expect to find any similarities such as you'd find between Portuguese and Italian, you can't even expect to find any similarities in how the net of words is divided (e. g. one word having what we consider very different meanings), but the words are short. I always found short foreign-sounding words (as in Chinese) easier to memorise than long foreign-sounding words (as in Greek). Also, the Chinese grammar is really easy compared to the grammar of Indo-European languages. One of my teachers even went as far as to say that Chinese has nothing that a student of Latin would recognise as grammar. What grammar there is is foreign however and in order to learn it, you first have to get rid of the notion that Chinese is anything like a European language - or that there are universal traits of grammar
Suspend the disbelief and learn Chinese grammar as if it was the first grammar you ever encountered. Be ready to just imitate authenthic sentence structures rather than try to form your own sentences from scratch for the first while.
The Beijing Language and Culture University offers 6-week intensive courses in Chinese which consist of about 25 times 4 hours of lessons. If you take a complete beginner's course there, you learn about 600 words, all Chinese grammar (except for things like word usage of words only taught at more advanced levels) and generally enough to get by in all tourist situations. You still won't be able to read long texts or have long conversations about e. g. school or the like, for the beginners' course they just focus on things tourists might need to say. I like their approach of teaching vocabulary and grammar through dialogues that are of direct practical use.
Studying 6 weeks like that is hard, particularly if you want to go sight-seeing and not spend your afternoons studying vocabulary
However, the atmosphere at the university with students coming from literally all over the world is fantastic and they do teach you more than I would have thought possible in such a short time. Anyways, this goes just to show you that yes, it is possible to learn a lot of Chinese in a short time, even as a beginner. And till 2008 you still have time, you don't need to try to cramp Chinese into your head in 6 weeks
Having lessons just once a week is not a good setting, because you'll probably forget a lot in-between lessons. Brain experts have found that studying 5 minutes every day is much more efficient than studying 1 hour once a week. If you can't change the class schedule, at least try to look at your lessons and vocabulary every day, even if only for a short period of time.
If you have any questions about learning Chinese or Beijing that you think somebody who was in your shoes might be able to answer better than a "Sinitic god", feel free to contact me, I'll be glad to. I don't presume to be able to correct your Chinese, for that you better ask one of the native speakers around, but I could share my experiences of learning Chinese and my experiences of Beijing with you.