Asperger's Syndrome sounds like it should come after you've reached a comfort level whether that means you're friends or bf/gf.
I feel this way because some people might see this as trying to gain attention and/or being self-defensive. Now, if you both are comfortable together, then you can tell her after dinner about how you grew up with Asperger's or something. She'll totally understand and even try to research/ask you about it. If it's just the first date and she doesn't enjoy your personality, then she isn't going to like you, Asperger's or no Asperger's.