As far as I know, knowing french will give you more "points" when they look at your resume, AC likes bilingual applicants. I'm not sure what knowing a language besides french will do for you but it's probably better than nothing.

Seneca looks like a great program, it's a lot of hard work mind you.. 4 solid years with no summers off. About 80 get accepted for the first year and less than half make it to the second. I was going to apply there for next year but I don't have 2nd year physics so I don't qualify (make sure you have it, I think calculus is a must aswell).. so i'm going to do Saults program instead.

Good luck with Seneca!