Majority of psychiatrists would not be able to diagnose it in adult. Getting referral from your university clinic or maybe even disability services will probably be best bet--the trainees would probably not be experienced enough. I was tentatively diagnosed by neuropsychologist in my university clinic but would have to go elsewhere to get it confirmed.There is a really good online community called wrongplanet.net that targets teens and adults on spectrum which is great source of information. Autism speaks is more for families with young children on spectrum.