Usually the right move is to contact recruiting as soon as the preference genuinely changes rather than waiting until interviews are underway.

Whether the office can be changed depends on where your application is in the process, how recruiting is coordinated across offices and whether the new office is hiring for your profile.

Explain the change briefly and give a real reason, such as family location, work authorization, language or a change in your geographic plans. You do not need to invent a strategic story about why the new office is suddenly your dream office.

Do not submit a second application just to force the change unless recruiting specifically tells you to. Ask the recruiter whether they can update the existing application and whether the change affects your current timeline.

I changed mine before interviews and recruiting just moved it internally. Definitely easier to ask early.