8 hours is a long time to spend in MEX, which is not a very nice airport. I used both the AA and IB lounges last summer, neither of which is very interesting. I marginally perferred the AA lounge as there was a partial outside view, and there was a larger choice of drinks (3 types of gin!). Food was poor in both. I don't think either have a dedicated F section.

I'd reccommend leaving the airport as you'll probably go mad if you stay there all day. I'm sure you can organise a driver and car for the day pretty easily. Go and have a walk through the Alameda, and then go up the Torre Latinoamerica for some great views. Might also have time to visit the Frida Khalo musuem.