Congratulations! Obviously Ross > Foster in terms of the program size, brand, and student body nationally but not so much in Seattle. I don't mean that Foster is amazingly supersedes Ross and there is a warp of space or rankings but that your opportunities become more equaled out and job search /network are comparable and while the pull of Foster is not as strong, I feel being on the ground near Amazon, Microsoft, FB, Google, and others is a strong benefit and if you can pass an interview with those recruiters, it does not matter as much which MBA program you went to as long as your experience checks out.
In other words, I think it makes sense for you to let 8 ranking spots drop and matriculate into Foster.
Your SO and their network will likely assist you with recruiting and internship finding.
I want to ping a few Foster folks
Norgay to see what they think and if they agree and of course I wonder what
souvik101990 believes...