...The nice guy who dresses like a cleaner hippie is going to get a lot more benefits from his fellow students in the future than the feminine hygiene product who treats people like dirt because of what they wear to class.
So, just upgrade the outfit to a collared shirt and some khaki shorts and keep the beard neat (but I use bandanas and head bands all the time, my hair is out of control, but it's important to me) and I should be fine until I interview?
Dress like you would have for class in undergrad.