Sundays tend to be the worst days in cities, you have the Sunday drivers that are going to or coming from visiting the rest of the family, and you will also find them on roads and highways, sometimes they will have vehicles that in reallity should not be on the roads,as in bad brakes, tires or general upkeep, so there tend to be more drivers that do not necesarily drive every day and tend to make more mistakes and cause more problems, otherwise early in the morning is best to traverse a city or arround mid day when some of them are at lunch.
Speeds in Mexico are lower than in the U.S. a lot of the big cities are old colonial and tend to have narrow streets and avenues, so they make them one way and it is sometimes a longer way to get to the place you want by having to travell a longer cirquitous route, ergo slower trafic and more time navigating to and from.
navegator