pursuant to RCW 46.61.502(5), Driving Under the Influence "is a gross misdemeanor."
And no, most first time offenders are not offered differed prosecutions. Unless they have a good lawyer, of course.
Actually, if you agree to a breath test if offered and are under about .15 you can request a deferred setence. You will need to have an ignition interlock in your car, admit you have a substance abuse problem and attend substance abuse counseling. but it is possible. The rules have changed this summer.
My wife is writing up the bench book for sentencing guidelines for Washington state this summer and it should be in the hands of your favorite judge by this fall.
The best thing to do under the current law (if you arn't too wasted) is to agree to everything, admit you have a problem and go deffered. You are pretty much garenteed to get off, albeit with several hundred $ of new electronics in your car and the prospect of not ever drinking again.