In quick summary of the barrens of Seattle:
Redmond is north-east of Seattle proper. In our world it is a pretty nice city, but in the SR timeline there was a reactor accident that made parts of the city varying degrees of radioactive, which drove away everyone who could leave, and given all the people that came into the plex after the breaking apart of the USA and Canada a lot of these newcomers ended up crowded into Redmond. It is the classic high density, poisonous, barrens. Historically a lot of support for Humanis came from Redmond and there were a lot of sections that were pretty biased against meta-humans; that may have faded by 2075 but its roots and reputation are as more of a human slum.
Puyallup, to the south of Seattle proper, was more rural/edge city before everything started going to drek. Parts of the place were covered by lava from Mount St. Helens, and more of it was buried under ash fall. Even in 2075 much of the place gets periodic ash falls, and high levels of sulfuric acid released from the muttering volcano. In the early years after things changed, a lot of people ended up in (the less poisoned parts of) Puyallup from sheer desperation/nowhere else to go. In contrast to Redmond, Puyallup had higher levels of meta-human settlement. The elven area at the south end has already been mentioned, and there is an old pit mine that is the basis of a large complex of orcish tunnels on its eastern edge. Although Puyallup has some mostly empty areas, it has high density sections too.
Google shadowrun seattle map and you should find a few different maps of the metroplex that should give you some idea of what is where. Bellevue is high class, everywhere else not mentioned is somewhat mixed, but each in its own way. The Wiki should be your friend for getting a sense of the cities.
