I've been vegan for a little over three years now (vegetarian for nearly a year before that). I wasn't interested in lucid dreaming before turning vegan, so I can't really compare, but as far as awareness goes, I feel the same. I generally feel better on every aspect, but it's hard to know if it's due to veganism as a diet, veganism as a mental process, or just completely unrelated.

Well, given the amount of lucid dreams I manage to get, I don't think veganism is bad for lucid dreaming at all.

What would be interesting is trying to find a list of every vitamin/nutrient which is thought to have an impact on lucid dreaming (I know B6 is one of them), and then compare the amount of said nutrients that meat-eaters and vegans consume on average. Then you should be able to say if vegans have better or worse lucid dreaming capabilities... but my guess is, if there's a difference, it's not going to be a big one.