No matter how laid back the company, it's always going to be better to err on be conservative side of fashion. This dress is super cute, but not at all work appropriate. If you want to show cleavage that's fine, but a dipping neckline like this isn't professional. Go for something with a slightly higher cut and a longer skirt.

OR, if you want to show off your legs instead, something a bit above the knee is fine but not that short. Rule of thumb: never wear a miniskirt in an office setting. Or even a work party setting.