Do the vampires have fangs when they bite or they just dont have them at all?

They don't have them at all. Stephenie explains about their fangs link.

"My vampires do not have fangs. Their teeth are so sharp and strong that fangs are hardly necessary (they could bite through steel, if so inclined–a human neck is like butter, ha ha). The non-vegetarian vampires don’t leave living victims (unless they are changing someone into a vampire); this isn’t the neat-and-tidy, two-small-holes-in-the-neck kind of vampire attack that you see in other vampire mythologies."

stephanie meyer's vampires don't have fangs and are nothing like vampires we used to, so everything you know about them (vampires from previous books and movies), all the myths,it doesn't involve stephanie's vampires.. so they don't have fangs but do have very sharp teeth with venom in it.. that's why edward doesn't french kiss bella, because she could easily cut herself..

twilight vampires dont have fangs because their teeth are already sharp enough thats why when they bite someone, it makes a cresent mark, not two little holes

Vampires are REALLY different in stephenie Meyers books, we wouldn't expect any vampires to be vegetarians would we, we thought vampires would be all gothic, biting humans, having fangs ect. But in stephenies books everything is different, thay can be vegetarians, they are not all gothic and THEY DONT HAVE FANGS AT ALL!!. xx Also instead of making 2 little holes like a vampire with fangs would, it makes a creasent mark.

Idek

yes but not in Twilight

No, those 'Vampires' don't have fangs.
Coming to think of this, having read some of the books and seen all of the movies due to being a movie/book reviewer for a local paper... I can, as a mythology fan as well as a die-hard horror story/movie fan, say I don't even see them as vampires.
Calling these creations vampires is like saying a white dog with black spots is a cow or a panda-bear: They share similarities, yes, but they aren't what you call them. I prefer to see them as disco-globe mosquitos.

Vampires do not exist so the question is invalid.