We have about four weeks, which is hardly enough to get well started. Our flight from San Francisco to Madrid is by British Air, via Heathrow—about 24 hours from take-off to the Madrid hotel (but nine of those hours attributable to changing time zones).
For us, Madrid is mostly museums. The Prado is having such a fiesta of Goya that El Greco, Titian, Ribera, and even Velasquez are hard to find. One could probably spend most of the month there. But could the feet and back hold out? And if one did do that, what else would one forgo?