If you have something specific in mind and can go in with pictures or fabric swatches, great.
Even though many registries provide cute little cards that go in with your wedding invitations, it's very bad etiquette to include these.
To make the most out of your speed dating experience, go in with an open mind and try not to have any preconceptions until you actually sit down and talk to the people at the event.
You can either buy the entire lot yourself or go in with friends and split the batch.
Though Costco opticians are knowledgeable and will be able to help you find the frames that fit your face the best, you may wish to go in with a general idea of what you'd like to try first.