Applying in person for visitor visa in Los Angeles

[RD11]

Hi,
I want to submit my application for Canadian visitor visa. I live in California, United State of America but an Indian citizen.
I am planning to visit Canada in 3rd week of December and hence, was thinking of applying for visitor visa in person in Los-Angeles.

1. For submitting my application package in person, do I need to have an appointment or is it just walk-in?
2. What is the processing time? Will I get an immediate answer on whether visa is approved or refused?
3. Will they mail back the passport? If yes, how long does it take?

Any help is appreciated. Apparently, they don't entertain enquiries through telephone.

Thanks,