I got rid of my beloved Goatie for my interview and I got the job on the first attempt. I'm not able to say whether I would have got the job with the beard but none of my pears have anything similar. 11 years later with the same company I have only seen variations on a full beard, smart hair long or short and no dreads.
The most important question is not how you feel about your dreads NOW, but more how will you create a professional persona with them. Will it be easier to make people think you are professional with the dreads or without.
A the end of the day GT has made a VERY valid point, look around to see what other professionals are dressed etc and use them as your guide. They have made it to where they are working so there is some valid guidance there.
Whatever happens and however it turns out good luck.
Si