Land at Portland Airport. Take the MAX Red Line (cheap) to Pioneer Courthouse Square, then walk to your hotel. I stayed in the outstanding Hampton Inn & Suites Portland - Pearl District - very comfortable, newly refurbished and nice-looking, and fantastic location, very convenient to everything. There's a great rooftop terrace with terrific views of the hills to the west and the Willamette River and city beyond. It's not cheap, but it's not outrageous either.
You'll be in Portland all 4 nights, so you have endless choices of outstanding food and drink. I ate at Trattoria Gallo Nero (exquisite and very authentic Italian), Andina (delicious and very interesting South American), and Pok Pok (Thai with famous fish sauce chicken wings, though apparently now closed!). For coffee, I sampled a different place every morning; grounded NW on Burnside sticks out in my mind as being particularly good with a great hipster/PNW vibe to boot. For beer, I visited Deschutes Brewery (based in Bend, OR) and 10 Barrel Brewing, as well as Quality cider bar, which is right across from the famous . Though I love beer, I confess I'm not an IPA fan at all, so I"m afraid the "Pacific Northwest craft beer" scene is a little bit lost on me. As for doughnuts: yes, Voodoo is the tourist staple, and I liked it just fine (definitely in a funky area!), but I honestly prefer Blue Star. Wild creations and outstanding flavors; the one in the Pearl District apparently no longer exists, but there are several others throughout the city.
On my only full day in Portland, I walked a wide loop, west up the hill to the International Rose Test Garden, which in May was filled with roses of every color imaginable. There are also commanding vistas over the entire city (and Vancouver, WA) and in clear weather you can see Mount Hood and even Mount St. Helens. If you continue up the hill, you can tour the exquisite Portland Japanese Garden; I had done so on a previous trip, so I didn't this time, but it is incredibly beautiful and well worth the time.
Another thing I would do if you have the time (though I wouldn't make it a huge priority) is walk across the valley and back up the opposite hill to Pittock Mansion, a stately home with more breathtaking views. You can also continue down the far side of that hill into Forest Park, which takes you on walking trails through gorgeous PNW temperate rainforest. Be warned, though, this is a LOT of walking, and will take a lot of time, so plan accordingly.
I headed back down from the Rose Garden. It was Sunday, so as an Anglo-Catholic I worshipped at the Parish of St. Mark, a beautiful building with astonishingly high-church practice. Afterward, I grabbed an ice cream at Salt & Straw (I didn't think it lived up to the hype) and headed back east to the Lan Su Chinese Garden, a serenely beautiful oasis right in the midst of the city. Nearby is Portland Saturday Market on the banks of the Willamette. This is a fun open-air market with all kinds of artwork and souvenirs for sale (high-quality, not tacky tourist stuff), as well as lots of different international foods to nosh.
You absolutely can't leave Portland without spending a couple of hours in Powell's City of Books, supposedly the largest bookstore in the world. It's right across from the aforementioned Quality cider bar, meaning the two together make a good way to spend an evening.