If you are Downtown, Pike is pretty much the only place within a short-decent walk. Elysian on Capitol Hill is nice, and there is a german bierhall/bocce court called Von Trapp's that has good beer. Six arms is run by McMinnamins (Localish Chain Brewpubs). Also, check out the Pine Box if you are going to be on Capitol Hill. It is a decent walk from downtown, and up a pretty steep (for out of towners) hill.
However, if I had one day in Seattle (proper) to drink beer, I would catch the bus to Ballard. There are about 10 different breweries in Ballard alone, and probably another 10 or so really good beer bars. If you only get a day, and don't have a rental car w/ a designated driver, Ballard is your place.
Other Neighborhoods with good beer (Best to Worst, but none are bad). SODO, Fremont, U-District, Greenwood, Georgetown.
But seriously, you could spend a week in the Seattle metropolitan area, do nothing but drink beer, and you would still miss a lot of good beer.
And +1 to the map that brewingrover linked. It is awesome.