I would think that French might be the best of the ones you have mentioned because it will be easier to find a French class.
I think that learning in a class is better than through tapes and stuff but then again I'm a nerd who actually enjoys going to school It's more fun in a class because you have other people there and also having to turn up in class and looking like a spazz if you haven't practiced is motivation.

How to learn a language - practice your vocab especially irregular verbs and use it as often as possible.
French is bit tricky because it is a gendered langauge. Everything is either male or female.

I'm looking for a Japanese class at the moment. I'm looking forward to it because I'm assured that everything is pronounced as it is written and that compared to the European languages I have learnt that the grammar is relatively simple (no genders yay!!). We're planning to go to Japan in March so I had better get a move on lol.