The site opens at nine and the coaches from Mexico City arrive around eleven. The hour in between is the one worth having, and the reason to sleep in San Juan or San Martín rather than in the capital.
Climbing is no longer allowed on the Pyramid of the Sun or the Pyramid of the Moon — the restriction came in with the pandemic and has stayed. What you walk is the Avenue of the Dead, two kilometres of it, the Ciudadela and the Temple of the Feathered Serpent at the southern end, and the painted compounds at Tepantitla, Atetelco and Tetitla off the main axis, which almost nobody visits and which hold the best surviving murals.
Balloon flights go at sunrise over the valley, which is the view the city was designed to be seen from. The air is only stable in the first hours of daylight, so a flight means a four o'clock start from Mexico City. Check the operator's pilots hold AFAC commercial licences, and ask the cancellation policy — weather scrubs flights often and a company that flies regardless is telling you something.
There is almost no shade on the site and it sits at 2,300 metres. Water, a hat and early hours are not optional.