I currently live in portland. It's beautiful.
The only issue right now is the weather!
I would do the following:
- Drive down the pacific coastline
- See Mt St Helens, Mt Rainier, Mt Hood, and even Mts Washington/Jefferson if you want to drive that far out
- See the columbia river gorge
- Go downtown Portland. There's tons to do there for free/cheap. A bunch of little parks that take up a block or two. There's stuff like the saturday market. Check out Powell's Books. Heck, visit reddit's /r/portland for more suggestions.
When I say 'see' I mean drive, hike, etc.
There's also plenty of great and often very cheap food, beer, and wine. Portland loves its beer culture (though to be fair, there's just as much good beer in many other places).