Quick Googling makes me think this is possible in Oregon without surgery, if you are under a doctor's care and living full time in your desired gender. But you probably should check what I'm saying.
Social Security has different standards - surgery is required for them. Not sure what surgeries are acceptable and not to them, though.
Changing your identification does NOT make you legally male. It changes your identification. Identification is not considered authoritative by law - it's evidence of the real thing, but the real thing (YOU!) trumps any identification in court. So the question becomes: What does a court consider a legal change? Most courts that have ruled want surgery (but they typically ruled in cases of MTF, not FTM). Some have insisted on the original birth certificate (corrected, re-issued, or whatever else did not count) unless it can be shown to be in error. Others have insisted on chromosomes. So it very much varies by location.
For instance, without surgery, I don't know of any location that has case law saying an MTF could marry a man (unless gay marriage was legal there as that would unfortunately be considered a gay marriage). Even if the MTF's DL says "F".
As for bathroom, it looks like you probably are okay using whatever bathroom matches your gender expression in Oregon (there's some debate, apparently, about whether a business can make you use a single-stall bathroom if they don't like you using the multi-stall one you are using). I personally don't think you would have a problem going into the mens' room with or without your legal ID being updated, but I don't have experience doing so, so I'll defer to other people on that.
All that said, it's still probably good to change your ID if you can. After all, your ID should represent who you are.
