Best route for commuting to Scarborough from downtown?
I pick up my new road bike this week. I'm very excited. The purpose: To start riding to work. I live at Queen and Broadview and work at Progress and McCowan in Scarborough. Now I haven't a clue which is the best route. A bike courier suggested taking Kingston Rd to the Danforth Rd, which eventually turns into McCowan. This is the most direct route, which clocks in at 18km. However, I wonder if taking the Don Valley trail would be quicker on account of there not being any traffic lights. Does anyone here commute to Scarborough or have any suggestions for the quickest and most safe route there?

I usually use www.ridethecity.com/toronto as a starting point and then tweak my route until I have something that works for me.
It will give you options for safer (but slower) routes as well as more direct (but higher traffic) routes. It might be worth checking out.
Also, someone might have posted a route on bikely.com or mapmyride.com
Biking to Warden and Eglinton along Bloor from the west end, I duck into East York around Coxwell and head north/north-east. O'Connor (and I think Coxwell) has a bike path but are also pretty low-traffic for rush hour.
Danforth curves up and turns into McCowan so you could get back on there and follow it. If you're going a little slower than cars, you'll probably only hit every second or third red. If you go the same speed as cars on any street, you can pretty well count on hitting the same reds as the cars.
Good luck!
Hi Rachel!
Well done! I would recommend, (as an off-road few-intersectioned route on a fairweather day) riding the Lower Don Trail north from the Queen Stairs, up past the Forks of The Don, and turning east to go up the length of Taylor Massey Creek to Victoria Park. From there it is on-road riding, and I would ride to Pharmacy, take the Pharmacy bike lane ("no one ever rides it" heh) as far north as you like, and then turn east. (There is a modicum of bike lane on Lawerence, but it's not for the faint of heart.) Perhaps Ellesmere? Otherwise, Danforth does indeed turn into McCowan, although traffic in my experience has been quite fast moving and disrespectfully derogatory to this cyclist (see my comment to Yvonne on Facebook).
Best wishes for great rides, and keep the rubber down!
Brian
Another route would be to go to the end of Broadview at O'Connor and use Beechwood to get on the trail, then follow the rest of the route suggested by Brian.
There's always the GO Train from GO Danforth (Main St.) to Scarborough, Eglinton and Rouge Hill train stations. For more, visit: www.BikesandTransit.com