Soon after that ride yesterday, the flags had to be moved to a different street after a last-minute change of venue to the Castillo du Chapultepec. No official reason was given, but the change was believed to be because of concerns about protests at the palace over Mr Pena Nieto's reforms to boost economic growth.
In particular, there have been objections to extensive changes to education which have annoyed the powerful teacher unions and coincided with the arrest of a union head for alleged fraud - although there are those who question whether it was a coincidence at all.
With so much on Mr Pena Nieto's plate at home, it was little wonder scant attention has been paid to the visit by Mr Key, who arrived in Mexico yesterday.
Mr Key had also changed his own plans at the last minute - staying to lead the Cabinet meeting that approved the Mighty River Power float rather than accompanying the rest of the trade delegation to Mexico.
The change cut his stay in the city down from two days to one. He used that day to push the case for greater access and investment to Mexico, which has trade agreements with 44 countries, although 90 per cent of its trade is with the United States.
Mr Key told the Mexican Business Council New Zealand companies were not only interested in exports to Mexico - they wanted to invest there to make the most of Mexico's easy access to big markets such as the United States and Canada.
He said the Trans Pacific Partnership - which now includes Mexico, Canada and the US - would help achieve that aim.
Mr Key also pushed New Zealand's case for return investment, saying it was rated as an easy place to do business, and had a liberal free-trade economy.
Few concrete measures were expected to come from the meeting with Mr Pena Nieto beyond a small announcement about encouraging small and medium businesses to invest in each other's countries.
But Mr Pena Nieta's media adviser, Diego Gomez Pickering, said the meeting was "symbolic" - not only because Mr Key is the first foreign leader to be hosted by Mr Pena Nieto but also because Mexico viewed New Zealand as a "strategic partner" in its plans to rebuild its foreign policy credentials.
He predicted a return visit would happen soon.