Yea.They can =].
If you're talking 'bout Twilight,i supose u already read BD and u know that they can.
And ..well,the other vampires ...don't know.I don't think.It seems like they don't have that "need".Saw it in a tv show =].
But on the internet,those who claim that they are vampires say that they have sex and have human habits and all of that stuff that we do.can surf the net if u want to know more :)),just sayin'.[i don't think those are like...true vamps]
yea they do remember in BD emmett and rosalie did it so many times( when they first got together). in the book esme made them a house but they keeped on destroying it. XD
Here's an answer from Stephenie Meyer herself.
Q. Can vampires have sex?
A. Yes. Don’t think I haven’t put a lot of thought into this one. I’m not going to get technical, but rest assured, it is entirely possible.
Got it from Personal Correspondence #6 on Twilight Lexicon.
If you haven't yet go & read the others they have. You'll learn some fun & new stuff! (Keep in mind they are from 2006 so they're kind of old now.)