Klingons are icky. I'm sure there would be plenty who would go for a Klingon but not me. All that posturing and yelling, and of course the actual injuries.
Vulcans, too much hard work.
Andorians, too adversarial.
Bolians, this seems good but there's the bowel rumours.
OMG I would just be a total weak ass at inter-species dating and end up with some round shouldered Bajoran!