Got conditional approval and went to book the interview for September when I'll be in Las Vegas (I live in Mexico) and Las Vegas is completely blocked while other airports aren't. How long do the interviews take as I can probably do a walk-in at DFW if the interview doesn't take too long or is it possible they'll open up appointment bookings in September?

Also, do they do the interviews on Sundays? (never mind on this, I found the Wiki.)