It's casual night out in a pub with dancing. I'd usually wear jeans. It will get very crowded later and it's turned hot here today.
I'm thinking of wearing a long loose cotton sundress, with wide straps. The sort of thing I'd usually wear for a lazy afternoon in a beer garden, but I won't be going out until the sun has gone tonight. The main reason for the choice is to be a bit cooler and to wear comfortable shoes! I don't really have an alternative. Other dresses are either "work" or "party". I expect the men will mostly wear smartish shorts, but I don't think that's right for a woman on a Friday night either?