Most Helpful Guy
You may run in to some people who treat you different if you're in an interracial relationship, but unfortunately it's just something that you'll have to deal with. I would imagine that 99% of the people you run in to won't have a problem with it (at least not outwardly) and the 1% that DO discriminate because of it are assholes anyway (or really old and from a time where things were different... can't always teach an old dog new tricks).
How likely is it to see a white chick with a mixed / biracial guy?
Pretty common... At least where I'm from, and I'm in the southern US.