Jet Blue is the best airline in America, bar none.
And yes, they welcome outside food. Remember once I hadn't been back to Buffalo for a while, on my to Buffalo International to head back to NYC, I called and found out the flight was delayed. Detoured at La Nova. Yep, brought on a large cheese/pepperoni pizza and just enjoyed it the whole flight home.
Mixed well with the vodka/iced teas I was making in the seat. Had the stewardess grab me a few bottles of Vodka in exchange for two slices. Great trade.