Generally though, guys are always acceptable in dockers or dress slacks and a nicely pressed sports shirt. If you are more comfortable in jacket and tie, or feel you make a better impression that way, go for it!!
Gals: Women are a different story. As usual, gals have come to speed-dating events in every attire from jeans to after-five. If in doubt, dress to impress or dress professional.
Both should wear a recent shower, mild amounts of scent, and good grooming. Unless you plan to sit on your hands, clean, clipped or filed fingernails are a must!!