In general Cabo is very relaxed and informal, khakis and short sleeve shirts are perfect for most places. As for girls, a nice skirt / mini-skirts, shorts and a top. Nothing really fancy. If you're out dancing depends on the place, there are a couple of more fashionable places, but anyway you can dress relaxed, no really need for fancy dressing. Just avoid shorts and trainers, specially for the guys!! Check this site, it's about Cabo's night life: Noche Cabo