Toronto is a great place to visit, but Toronto and the surrounding cities are not bicycle friendly. So unless you have a specific reason to visit the area, consider taking public transportation around or through the Toronto area.
To get into Toronto, the "Go Train" is probably the best bet. It runs between the outlying areas to the city core. A couple of years ago, rather than ride through the city, I took a 15 minute Go Train ride to Scarborough, where I began my tour along the north shore of Lake Ontario toward Kingston.
You can travel right across Toronto, east - west, by subway, but you cannot have a bike during morning or afternoon rush hours.
A patchwork system of bicycle paths and lanes exists in Toronto, but it's not easy to get from A to B unless you know the city well. Along at least one route, bicyclists share a lane with buses, taxis, and any vehicle that needs to make a right turn!