I assume you are a Washington Resident. If so you really don't have any choice as to where to go.
1. If you are the resident of the City of Spokane (or any other city) you CAN go to that police department of the city you live in, or you can go to the County Sheriff's office.
2. If you live outside the city limits and are therefore not a city resident, your only choice is the County Sheriff of the county you live in.
NON Residents on the other hand can apply at ANY county sheriff's office.
Typically (In most counties), the Sheriffs office is the better place to go vs the City, but YMMV. I am not familiar with how the Spokane County sheriffs office is on this matter. I am fairly sure the City will make you wait the full 30 days.