"For a person who is living and working in US, but is not US permanent resident, can (s)he apply Canadian permanent residency from Buffalo, or has to go back to the home country?"
If you feel that you will be able to stay legally in US for 18-24 months after sending your application, then only you should submit your papers for Canada immigration to Buffalo. You know your situation and plan accordingly. If you are applying Canada immigration to get a job in IT, Please don’t apply, Canada has no IT jobs at this time, If you have other reasons you know better.
