[@Aphelion] I'm with Prints, Castelia does seem like your best bet.

Along with the other cities Prints brought up, I'd also like to bring up Celadon city: Maybe not the biggest place but business based would work and it's been shown to be becoming more polluted, not with the Grimer infested water and all, but we can assume isn't too awful since we've got Erica there as well. Personally though, I think Castelia works best.