We have to be a little careful about dragon legends: Most modern depictions of dragons are rather dinosaur-like, but these are post-rationalizations in an age where we
know about dinosaurs. Traditonal dragon pictures are much more serpent like. They could, however, be inspired by findings of dinosaur skeletons. Such findings have of course happened all through the ages.
About coexistence of humans and dinosaurs: The basic question is really if you believe in Genesis or Science. From a scientific POV, the idea is absurd. We are not talking about little imprecisions in dating methods here, we are talking about 60 million years.
Hans