I just flew MIA-JFK-LAX in F on Saturday, and I had FL and FFD access in Miami. Both were offered when I scanned my boarding pass--I did not have to request it as a special dispensation. The fact that FFD opens at noon at DFW may limit how much you're able to enjoy there, but access won't be a problem. I will say that the agent at the first desk downstairs is the one who proactively offered it. We arrived before FFD opened, so we popped back out to the upper lobby at 1:00 to request FFD admittance, and the agent there took a bit more time sorting out how exactly I had access. YMMV.