Dreadlocks in the work place
If you are growing them for any type of spiritual reasons, you are protected by the first amendment. No employer is allowed to not hire or fire you for them. That said, I don't know everything about Oregon's Laws. If it is am "At will" state, they don't have to give you a reason to not hire or fire you. It's up to you to prove that your locks were the reason. I live in Pa, and we are an At Will state.
You could always tie them back for the interview. When in a ponytail, it's usually hard to see they are locks from the front. Ad they look neat and orderly. If you don't want to tie them back, of if they aren't long enough yet, you can get a plain black tam. Tams are generally professional, at least if they aren't bright and colourful. Black ones look nice and hide everything. Plus women are usually expected to have some sort ofaccessorywith their outfits.
And if they question you about a religious motive, you are legally allowed to refuse answering them. Any questions about religious beliefs are strictly illegal to ask.
Plus, if you are qualified for the job, and have goodreferences, you will be fine.