September is the sweet spot for the Pacific Northwest. The summer heat fades, the heavy crowds head home, and the trails at Olympic and Mount Rainier are finally quiet enough to actually enjoy.
A trip like this usually runs about $2000. You can cover this by using the Discover it® Cash Back card, which offers 0% intro APR for 15 months on purchases and balance transfers. This gives you a way to spread the cost over a year and a quarter without paying interest.
That 15-month window is a firm deadline, not a gift. If you still have a balance after the intro period ends, you will start paying interest on the remaining amount, which will cost you extra.