If you visit that neighborhood today, you can see the results of laws very different from those in American suburbs. Most of the houses have been expanded. Each one has grown in a different way. They've been repainted different colors, there are Virgin of Guadalupe icons and paintings and Aztec designs and decorations and every other kind of individualistic expression all over. Small shops have opened to provide typical neighborhood corner store services and light industry like auto repair and electronics servicing is going on during the day. Lots of the car parking has been enclosed and some has been eliminated entirely in favor of more living space. [1]

All of those changes would be illegal in the vast majority of American suburbs. When older American cities were built, the laws were more like Mexican laws and neighborhoods could grow up with residents and families and provide local services and develop character.

Plus, the Mexican neighborhood and older American neighborhoods are significantly denser than new American suburbs, without being remotely like really dense development. That makes things much more accessible by walking and creates more cooperation.

That's the difference a reasonably open and humble set of laws makes.

[0] http://www.nationalgeographic.com/photography/photo-of-the-d...

[1] Try a satellite or street view somewhere around 19º18'30'' N and 98º51'30'' W