Hi Maestro,
don´t know anything about the Visas, you gotta ask some office in Canada.
As for the rules- no problems. Personaly I think some of the rules in USA are stricter than here.
As for Prague sightseeing- send a PM to Pisis. He lives in Prague and if I am not not wrong, his girlfriend (wife?) works for some travel agency in Prague so I´m sure he will be able to help you.
I´m sure you´ll enjoy your stay in Prague as this town has a long long time hitory with a beautiful architecture. I´ve visited a lot of European cities but nothing´s gonna beat Prague and Paris...
I never felt in danger in Prague...the most scared I was 3 years ago- in a subway in Brooklyn
But nothing happened to me...