I am an IB student from California and I just wanted to know what the opinions on IB was to the UDub admissions. I am hoping it will boost my chances of getting accepted because this is my top school. Please let me know any ideas on if it will help or what exactly they think about it. Thanks so much!! 
Like all schools, UW considers academic course rigor in the context of your school environment. So, if you took challenging IB courses and their corresponding tests, it will certainly show well on your application, especially if you did well in those classes/tests.
Best of luck!
On a side note, do know that UW only accepts HL tests for transfer credit, and not even all HL tests. I only received credit for American History HL and English A haha. (no Business and Management! :(( )