Early to mid October can be very good in the Toronto area, actually best north-west of the city, Hockley Valley, Shelburne, Caledon Hills, an hour's or two's drive.
Can't answer about St. John's. My feeling is that Oct 23ish a rainy time of year there. But there are many scenic spots within easy drive of the city in any direction.
Late October in Toronto is normally late for good fall colour, although what's left can also be interesting. But maybe driving a bit south, to NY, might still be colourful, not sure that NY is south enough though. I assume you mean upper New York state, not NY city. I drive through the Adirondacks to Lake Placid on the first November weekend once and the scenery was beautiful even though the main colours were over, but that's quite far from Toronto, not a convenient weekend drive. There are hilly areas south of Buffalo, closer to Toronto, but maybe someone else can help there.
Thanks for the Toronto suggestions Robert!
I actually was thinking of driving to NYC. I've spent so much time in the GTA for work this year, I thought about heading to NYC for the weekend - I've heard central park is nice in the fall, but not sure if its too early or too late.
I've only got one day in St. John's for myself. Any suggestions on best places to hit given the limited time I have?