I've lived here 4 years and still haven't been to them all so, that might indicate how hard of an question that is to answer!
Are you going to be able to get around town fairly easily? Car? Transit?
Up in NorthEast you've got Widmer, which is big commercial, but the tasting room is pretty awesome with a lot of experiemental draft only offerings. Just up the road from them is Ecliptic (John Harris) that's very tasty. A little further up Mississippi is Stormbreaker which is also pretty good.
Up in Northwest Industrial there's not a whole lot of breweries (although that is changing). Breakside just opened their slabtown location, and Sasquatch is open now on 32nd avenue. A couple of places I really like (I work in that neighborhood) are the Abbey Bar, great draft and bottle Belgian/Euro beer selection and the McMenamins 23rd Ave Bottle shop, which has a pretty good selection.
In SouthEast I would recommend Zoiglhaus and Montavilla Brew Werks. Unfortunately the places in SE aren't as closely packed together. Inner southeast has Laurelwood, Lucky Labrador and a handful of others.
I don't even know what's in SouthWest right now off the top of my head. Not a lot.
In downtown you have several of the bigger/older places to choose from. 10 Barrel and Deschutes have brewpubs in Downtown along with Bridgeport (which is not doing well as of late) and Fat Heads.
That should get you started. Enjoy your trip!