How do you solve a problem like Sigüenza?

I don't know what to do about Sigüenza. I just got into Brihuega after having come up from Sigüenza, and while I think I'll post the route as I did it, I have to find another alternative.

The easiest and most direct way to get to Brihuega is to leave Sigüenza by the CM1101 highway, go straight over for 25 kilometres, climb out of the Henares Valley and, once you reach the A2 motorway, take the service road to the turnoff that gets you onto the N204 highway. Under the bridge, on the roundabout, second road on the right and bam! Next thing you know, you're averaging 25 km/h to 30 km/h on a slightly hilly highway and, in less than an hour, you're there.

This makes it sound far, far more straightforward than it actually is. The highway that links Sigüenza with the A2 has a lot of traffic (and, admittedly, a fairly wide shoulder), but it's the climb up out of the valley just before you get the A2 that's fairly hairy. You are required to climb 200 metres in fewer than 4 km, on a highway where most drivers do not respect the speed limits (well, they do if they're driving older cars or trucks, but that seems to be more out of necessity than any sense of civic responsibility.) And -- there is NO nice way to say this -- the highway is FILTHY. The worst offenders? Bottles for water and soda which are filled with some kind of yellow liquid which I can only assume is urine. And since most women do not have the bodily control to emit into bottles like this, I can only assume that this means that guys are relieving themselves IN THEIR OWN CARS and flinging the bottles out of the window, for the rest of us to deal with.

I'm not saying that cyclists shouldn't go to Sigüenza. Rather the opposite. It's just that there has to be a much more pleasant way of leaving it....