Portland is located just south of the confluence of the Willamette and Columbia Rivers. The Columbia River is flowing from east to west to the Pacific ocean. The Willamette flows from south to north. The Willamette divides Portland into "east" and "west". The airport is to the east. Portland is divided into "north" and "south" by Burnside street. This gives the four quadrants you would expect. The conference venue is in southwest Portland, being south of Burnside and west of the Willamette. (There is a fifth "quadrant" called north which is east of the river but west of the north south line that goes through the river at Burnside.)
The red line of the MAX train (http://www.trimet.org/) can take you from the airport to the heart of downtown. Purchase an "all zone" ticket for $1.95 from the automated kiosk before boarding the train. To get to the conference venue I recommend the Morrison, SW 3rd Ave stop, and then walk south. The hotel is about 8 blocks south and one block east of the 3rd and Morrison stop (less than half a mile).
The conference venue, the Portland Marriott Downtown Waterfront, is on the waterfront in southwest, at 1st Avenue and Clay. The Portland State University campus is a few blocks south and several blocks west. The central campus extends from Broadway (logically 7th Ave.) to Twelfth Ave and from Jackson Street to Market Street. See http://www.pdx.edu/map.html. The area between PSU, the conference venue, and Burnside is commonly called "downtown."
There is a streetcar http://www.portlandstreetcar.org/ that runs from River Place (across from the venue), through the university, north through downtown on 10th and 11th Avenues, past Powell's Books, and into northwest Portland. Where it crosses Burnside it enters the Pearl district, a recently gentrified former industrial area. In Northwest Portland all streets are in alphabetical order (Burnside, Couch, Davis, Everett, ...). The streetcar continues on 10th and 11th until it gets to Northrup and Lovejoy, where it heads west to NW 21st and 23rd.
Other links of interest: