I'm traveling on December 2, and I will arrive in Lisbon December 3 for 6 hours, from 6 a.m. to 12 p.m., and then catch my other flight. Do you think I would be able to get breakfast early this morning, and then catch my flight? if the time allows it?
I did this before. The airport is a short ride from the center on the subway, so it's entirely possible to go to the center, wander around, and get back in time for your flight. It might be tough to find anything at 7am, though.