First, congratulations on being accepted into USC and WashU. Both are fantastic schools. Since you already have knowledge of Los Angeles, I'd start by asking the following: are you looking for the next few years to be in the same city or are you looking for a change? If you're looking for a change, I'd recommend starting with the St. Louis, MO thread in the City Forums here. I'd also recommend reaching out to current students to see what it's like working with specific professors.
Lastly, since you've been accepted to WashU, the following links might be helpful: https://gradstudies.artsci.wustl.edu/news/office-graduate-studies-launches https://strategicplan.artsci.wustl.edu
It seems like a lot of change is coming soon.