Even in business, business casual means a lot of things. On the East Coast its likely Dockers and going tieless. On the West Coast I've seen it mean flip flops and shorts that weren't cut offs.
What they want is for you to show up clean and tidy - perferably in clothes you'd wear "out." It doesn't mean "go to a wedding" dressup (though you can get away with that), but it doesn't mean "I last wore this t-shirt to cut the lawn in" either.
No muscle shirts, no short shorts, no tube tops or halter tops. Nothing appropriate for Sturges. Resort shorts (i.e. longer shorts, skorts) would be OK, as would nice jeans. Dockers would be great for both men and women.