Wow, my mind was so not on pairing/sexuality stuff on that one! XD;
Conrad -- depends on his mood. Thanks to his teenage-hood (or the equivalent) when he's upset he tends to just go for whatever's attractive, available, and unlikely to attach. For someone he'd actually consider a relationship with, he's into... innocent types. Not necessarily naive, though that does seem to go along.
Lacus would say that she doesn't really have a type, since she loves everyone for who they are, blah blah. For real, she likes strong guys who are strong in spite of their pain.
Saya has a thing for protective, silent types... at present. But she's still evolving, so we'll see how it changes.
JD has such eclectic tastes, but whatever else she is his ideal woman would be a serious dork.
Anew is hard to gauge since she was made the way she is, but if things were different I think she'd be drawn to people who gently lead her.
Cross, in terms of considering an actual relationship, wants a sophisticated woman who can keep him on his toes. Attitude, but eloquent attitude. And of course the looks and cleanliness are a prerequisite.
Is there any circumstance ever in which Allen would let someone beat him at poker? :D