It's always New York. Before 2012 it was allowed to be DC, but since the first Avengers movie New York is mandatory. (The Tron trailer is devoid of landmarks, which makes me think that they plan to be indeterminate about what city it is. I could be wrong.)
I think you're right, Tron takes place in a fake city called "Center City"
Center City is essentially a mixture of LA and Vancouver standing in for LA.
One would think from the name that Center City would be a Chicago expy
Well, subbing for LA it had to be on the west coast. And assuming the house seen at the start of Legacy is outside Center City, there’s a US flag raised outside, so it’s not fully a Vancouver substitute, either, despite having an almost identical layout.
So, perhaps “center of the west coast” is the meaning meant to be extrapolated from that.