We live in the Pacific Northwest; our 'dressy' is called 'casual' by most of the U.S. :D
We wear: nice (not stained or dirty) pants or skirts, shirts with sleeves (short sleeves OK) and no cleavage (not turtlenecks, though, just no cleavage). Some wear their sleeveless dresses with a little cardigan. The men mostly wear pants or nice jeans with a collared shirt tucked in, though we have a few guys who can pull of the three-piece suit with aplomb. The kids and teens wear slightly more hip versions of the above.
We do have a few that dress more modestly, but most wear the above. Certainly a guess would not be expected to be dressed more modestly than the above, though no one would bat an eye if they were.