Stay in Seattle City limits and you should be fine. My favorite dispensary has gone down two times now.....once in Shoreline and once in Bothell. Shoreline put down a moratorium and asked him to shut down, in Bothell he was "raided" but no charges were filled. He has moved to Seattle now where the LEO's are friendly.
The dispensary's in Seattle are welcomed and medical patients do not get busted....but don't step foot out of Seattle as no other County/City is as friendly......yet.
Also, I would wait and see what our legislature does with SB 5073. They are writing up guidelines regarding dispensaries that if passed will take effect July 1st. There is rumor of a "lottery" type selection of licensing, so that would be something you would want to try for.. if indeed that is what they decide.
Either way, I think it would be worth holding off to see what happens with SB 5073. It would be a bummer to make the investment to get all set up and then not be drawn from the lottery.