Does anyone NOT believe that objective truth exists?

There's no reason objective truth cannot exist. I think what you're asking though, and the better question, is can you ever hope to determine an objective truth. I think it depends on what you accept as a baseline. Consider your red light example and a few baseline assumptions one could make:

• assume science as we know it within the realm of sanity is accurate - most humans are sane, these humans witness events like stop lights and agree that a truth value can be obtained, they are on or off, red or not
• assume science only - you know red lights exist and are aware of their on/off states, but just like the crazy people in hospitals that who think people are hiding in the corners of their rooms, things you witness, even on a grand scale, have a probability of giving false positives in terms of truth, i.e., maybe the light is red, or maybe i'm crazy
• assume nothing - as far fetched as it seems, you can't disprove that you don't live in a world like the one described in The Matrix ... i.e., you think the light is red, and everyone you know agrees, but there is a chance that everything you know and process in your brain (or whatever) only resides there, and is 100% fabricated, it's really not too far-fetched of a concept given the dreams humans have and the realism during the dream

... so, to answer your question, I believe objective truth can exist, however, I don't believe humans have the capacity to realize it. I do believe that you can assume certain things away and arrive at a useful degree of widely accepted truth, but I think it is simply not possible to ever validate a universal truth.

Technically, the non-existence of objective truth doesn't imply that driving on the right side of the road "doesn't matter".

Just because the oncoming car I perceive doesn't objectively exist doesn't mean that I won't subsequently perceive all the negative results that follow from driving on the wrong side. Subjective reality is still reality.

That said, I have a very difficult time articulating where I stand on the question. As phrased, it's probably too simplistic to simply answer "yes" or "no", nor am I particularly convinced that it's "impossible" to know.

Most of the time, I operate in the "naive realist" mode of science. I'm agnostic with respect to the question of whether our sense experience is direct experience of an external reality, but it seems foolish to deny that there's some "real" reality out there that affects our sensory experiences.

I guess that leaves me somewhere in the neighborhood of neo-platonist idealist.

Except on leap days, when I indulge myself in pure solipcism.

This is essentially Wittgenstein's response to philosophical skepticism (on which The Matrix and similar scenarios-- brains in a vat, etc.-- are based). He argues that, if you trace back the chain of evidence for any empirical belief, you ultimately come not to a well-founded belief or an ill-founded one, but to an "unfounded way of acting," which is not based in belief but is the basis of it. If we want to function, we must act as if we had reliable evidence for certain things that we really don't-- as he says, "If i want the door to open, the hinges must stay put."

So, he argues that the skeptics essentially misunderstood the situation, because the it's not that the fundamental aspects of reality seem real to us because our reason has been fooled; we don't subject these things to reason in the first place. The whole application of "evidence" and "doubt" to these beliefs is, basically, a category mistake. So, stopping at red lights is, in a sense, unfounded, but you're not actually ever looking for evidence that you should stop anyway.