Hello Seattle,
I'm planning on visiting next month
 (mid-March). Just curious to what websites are best for advertising.
 Any help is greatly appreciated  

I'd recommend emailing specific providers and asking for advice. That's what I did and I found everyone to be super friendly and beyond helpful!

I've found that especially for visiting new cities advertising on Eros is the easiest as you can copy ads and you can choose what days you want them to run from.