All taxis in Monterrey are painted green, most are VW, nissan or little chevy, please avoid to take taxis with black windows, just for safety, and be shure to see the taximeter running at the beginin, is better if you ask for taxis in the front desk, prices are similar to free streets taxis
The locals drive fast and they do not want to let anyone in front of them. Horns are blasted very often, and with a particular fury. Funny, as the people of Monterrey seem so gentle and thoughtful when they are not behind the wheel. There are also quite a few older vehicles on the road. This is a photo of Benito Juarez Avenue in the city center, but not at a particularly busy hour.
Mexican traffic is an adventure with its own set of peculiar rules and takes some getting used to. Non indigenous drivers may want to be careful or leave the driving to a local if possible. During the wet season (September) conditions may change in the blink of an eye during thunderstorms that turn the streets into rivers in an instant. Driving becomes all the more perilous, especially when driving smaller town cars among the larger trucks, semi's and buses that crowd the streets. From personal experience I found out these can be sent floating around.
Having lived here for an extended period of time in the mean while I am able to shed some more light on the subject. I have been able to observe that due to the utter and complete disregard for any and all traffic rules (in fact the standard driving style, at least in Monterrey, is summed up in the list of infractions on a traffic violation ticket) venturing into traffic in this city is tantamount to playing Russian roulette. Red traffic lights will be regularly ignored for instance which has led to my witnessing several near misses which would undoubtedly have turned out fatal. The ignorance about the traffic code is only surpassed by the complete indifference for personal and public safety. Drivers will do anything at any time in any way they feel like, without any concern what so ever for their fellow transients. Taxi drivers excel in this which explains why they're involved in about at least 85% of the accidents.