If you want to upset French language purists, learn to speak Chiac. It's a dialect of Acadian French spoken in New Brunswick that borrows liberally from English. Even as other North American dialects and languages are vanishing, Chiac seems to be sticking around.
If you want to learn English as it's spoken, you have to practice phrases like "the guy's a total flake." That's how students learn at UCLA Extension's American Language Center, where the slang is snappy and up-to-date.