cape Breton island in nova scotia is amazing, but I guess that's a bit northeast of Halifax...
I couldn't tell you much about Toronto, only been there a few times and im not so much familiar with the city.
I lived in Ottawa for 3 years in highschool, really not too much exciting there. I wouldn't recommend it.
quebec city... its alright. I suppose its worth checking out. there are a few cool spots I found around the city.
Halifax is probably my favourite of the above mentioned cities, you might come across squats. I recommend checking out the arc, its a drop in centre run by two really kind women, Dorothy and Emily, on Gottingen st. its a sweet place, they have photographs of all the travellers that came in over the years all over the walls, in the basement they have washers and dryers you can use and have signs that people have used for flying signs/spanging plastered all over the walls and some are pretty creative. you can shower, eat good food, make patches, read, talk to whoevers there, get clean socks. its somewhere I always stop in Halifax.
between Toronto and Halifax.... there is not so much breathtaking scenery if you stick to the main hwy. gaspesie in quebec is supposed to tbe really good. PEI was a bit boring for me but nice for beaches. newfoundland is beautiful, people are funny and pretty kind.
new Brunswick is pretty average IMO, cities boring. you could check out the bay of fundy, the tides there are pretty shocking.
have fun!