I'm almost in the same boat! My full commute would be 21 miles. I bike-train-bike 7.5-?-3.2 to work (reverse for home). My full commute takes about 90 minutes including the train ride, but that's on a mountain bike and it is HOT here. In the morning I try to go easy so I don't wind up smelly at work (we have a shower but it is supposed to be for emergency use in case of chemical spill and it's roach-infested anyway), then in the afternoon there is more traffic and even more heat. My ride home last week was 108 F.

I figure if I biked the whole thing it would probably take me a little over 2 hours because it's 100% urban sprawl with lots of traffic and lights.