Sadly, even if dismissed - under Washington State Law - any prior DUI that was amended to a Reckless Driving like yours - counts as a prior DUI if you get another one in seven years. You'll want to consult with a DUI attorney immediately.
Every case is different, and this is not intended to be anything other than helpful information. This in no way creates an attorney-client relationship between us. If you'd like to speak further about this answer, feel free to call me for your FREE CONSULTATION at 425-424-9401.
I have successfully argued that the prior does not count. The deferred statute parallels the vacate statute which releases you from all "penalties and liabilities" from the conviction.
At your service,
Violation date to violation date. If the first case is within 7 years of the new one and it was a DUI reduced/amended to anything and even a deferred prosecution that was dismissed, it counts. Get an Attorney.