That depends largely on the sign or signal; I can't think of any around here that could apply to many bicycles (70mph speed limit on an uphill stretch is pretty much wishful thinking) that aren't absolutely appropriate for bicycles to follow as well. I don't think I'd ever have a strong urge to violate any traffic laws on the bike if they'd just fix the traffic signals. (Texas has no provision (that I've found - if someone has a cite, let me know) for presuming that a signal is malfunctioning unless it's off or flashing, so if the bike won't trip it on my 3AM rides, the only legal choice is to wait an hour or more for a car to come along going my direction.)