Lonely Planet Pocket French Phrase Book
I remember trying to speed-learn French for my first trip to Montreal. I thought I'd need it there.
When I did try to speak French with Quebecois there, it turned into a disaster and I ended up sounding like Clark Griswald in National Lampoon's European Vacation.
On later trips to Montreal, I gave up on the French and just spoke English everywhere, just letting everyone know that I'm a dumb American tourist.
For me at least, nothing can replace a brick and mortar classroom with a human instructor. Online courses, Learn French in Your Car, CDs, pocket French books, etc. are OK, but they don't stick.
I would recommend taking a class at a community college and using the language everyday. Talk to other people, talk to yourself in both English and French; until it becomes second nature.
I'm actually thinking of taking a French class at a community college myself. Some of the SPs in Montreal can't speak English, so I'd like to be able to talk to them.