Parking Garage - can shoot both runways though north runway can be shot regardless of wind direction, south runway best if arrivals are from the east.
Marine Drive - various spots along entire length of 28R, there wide shoulder at about midfield you'll usually see cars parked at.
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Photo © Bill Shemley
NE 33rd Drive at Marine Drive - with a long lens you have a great view straight down runway 10R and if weather is good Mt Hood directly behind.
If you have a big truck or something to stand on the cell phone waiting area might work near the end of 28L but with a fence in the way.