Hey, whatever we suggest, you're going to have to figure it out for yourself. I too ride about 6 miles, but in New Jersey. My problem is that I sit on an overheated train for an hour, then go out into the freezing cold and get on my bike. That initial blast of cold air is brutal! But that chill lasts only a minute or so. But within a mile or so that feeling has gone away, and another mile later I'm unzipping.

Anyway, my thinking is: if you're sweating anywhere, it's because your body is trying to lose heat. Your body will do this better with one less longjohns. I don't believe your legs will be cold at all, and certainly not for long enough to worry about it. As for shirts and windbreaker, hshearer makes a good point about trapping moisture, but I still think a better solution is to sweat less. I wouldn't want to ride without a windbreaker, mainly because my current windbreaker is extremely visible and reflective. Go with the more reflective option!

I've recently switched from a pullover style fleece to a zip front fleece, and am happy with the result. As I get hot, I unzip more.