Dead end... or is it?

I commute through this street each weekday. On most days, I tend to ignore this:


Whenever I continue to strive northward, despite being informed that it's futile by that rather unwelcoming, depressing traffic sign, I soon see this:

Clearly, for me, a bicyclist, the dead end sign signals false information. Had I not chosen to disobey that particular traffic sign one day, I would never have found out that there is a better route between A and B. My one way commute would take two minutes longer. By using a faster route I can now save some 20 minutes each week. That makes nearly 18 hours a year. I get an extra day each year! Choosing to ignore dead end signs clearly pays off.

Now, my question is: as a bicyclist, what other traffic signals can I choose to disobey? Or perhaps, should I just regard all traffic signs as more of recommendations and hints than actual orders and regulations?