OAXACA DE JUAREZ, Mexico — The zocalos of Mexico are in many ways what New England town greens once were, places where townspeople come to socialize, find shade at siesta time, and listen to concerts in the evening.

In Oaxaca de Juarez, it is also where tourists often start their daily explorations, and where peddlers, beggars, and black-market moneychangers chase them.
 
Oaxaca's zocalo is ringed by a couple dozen very tall, very old trees, guarded to thigh level by green wrought-iron fences and to eye level by a white chemical protectant. A well-kept gazebo is the centerpiece; walkways crisscross the square, and greenery further divides it into conversation pits.

Although the streets elsewhere in Oaxaca are dirty, the cobblestoned streets around the zocalo are uncommonly clean.

That's thanks to Marcelino Hernandez Castro and a crew of compadres. Each day, each using only a pushcart and a couple of brooms, they sweep from one end of the square to the other.

Most of the custodians wear just anything, but Hernandez arrives each day in a straw hat, tan chinos and a button-down shirt. He also brings dedication and a simple method.

Using an enormous broom with a spread larger than a peacock's feathers, he begins with broad strokes: Long stride, extended reach, full follow-through. Then, using a smaller model, he goes back, for the gutters and to touch up. From one end to the other, from morning until after nightfall.

Considering that one political party has dominated Mexican electoral politics for most of a century, political expression thrives in Oaxaca, particularly these days because of the Zapatista movement in the neighboring state of Chiapas.

Political graffiti -- or wide swaths of mismatched paint where graffiti have been covered over -- is on practically every building in the neighborhood. The covering up could easily be a full-time job; ideas that appear by morning can be gone by afternoon.

Some graffiti is allowed to stand, but apparently only if it offends no one in power. Some last a few days, such as "Death to Roberto," which was on a school building a couple blocks from the zocalo and apparently targeted a candidate for student council.

When the sentiments are most rude to the ruling powers, and when they are posted in the rudest places, such as on every ground-floor panel of a government office building across from the zocalo, the cover-up is done with rollers instead of brushes, so it looks more like a new color scheme than the voice of the people, squelched.

High-glossing over graffiti is one thing, but silencing amplified loud speakers is much tougher. That's no doubt why, on a recent Monday night, hunger strikers seeking justice for the working classes blared their message at one end of the zocalo while young members of a left-wing group, the vanguard of hundreds of marchers en route from Chiapas to Mexico City, sang out their politically charged message at the other.

The next evening about 5:30, as Oaxaquenos, tourists, and bused-in supporters lined the square, the marchers strode in, chanting slogans praising the Zapatista leader ("We are all [Subcommandante] Marcos, Marcos is all of us"), carrying banners and turning left at each corner until they had encircled the square.

Then they moved inward toward the gazebo. March leaders clambered up and began two solid hours of exhortations. The energy in the air easily exceeded that of most US political rallies. That night, the marchers slept on the zocalo, after a boisterous evening of eating and mariachi entertainment.

In the morning, the marchers re-formed their ranks and headed off for the national capital, leaving behind a challenge for Hernandez so substantial that a modern, garbage-compressing truck was brought in. But his task was delayed even before he could begin. No sooner had the campesinos left when another cadre moved in, striding boldly, chanting loudly.

It was Oaxaca's first-graders, demonstrating in support of the fifth annual national health week.