"The Plaza de los Mariachis, just east of the historic center, is a good place to get a taste of it, but it is unwise to linger here after about 9pm. Most tourists now get their mariachi experience in one of the sanitized (but safe) venues provided for it's purpose." --Lonely Planet
We found the historic Plaza de los Mariachis quite by accident. We were strolling along hand in hand through Zona Centro just past the cathedral argueing about whether one could or should interact with public art. I was insisting that public art shaped like chairs in the center of a plaza is just asking to be sat upon, but he argued the sanctity of the bony bronzed creatures.
In mid-debate we noticed the disintegrating, vertical, orange and yellow 'Teatro Alameda', but then followed the letters down below to the scarcely lit street where a few bloated silver buttoned suits stood shipwrecked upon the median. They were the loner mariachi, the stragglers, and at the street intersections and corners they showed no intention of crossing. It seemed strange and surreal to us that the scattered men should be standing solo without a troop of comrades; we shivered at the lonliness of them.
As we advanced toward the pimps and the teatro, the squads of musicans began to solidify and cling together along the plaza lining. After a block of this reception, we came upon a tree filled courtyard with lights strung across the top, and yellow SOL umbrellas attached to white plastic tables planted below. As luck would have it, some wealthy mexican locals had gathered a party, and a band of ten or twelve musicians had them surrounded with brass, violin, guitar and belting vocals while we snuggled up beside them to absorb the decadent serenade.

When the guide books say that this territory is dangerous, it does not mean you are surrounded by knives, or guns, or pickpockets, or sexual deviants (but BYO-TP). This place is dangerous because it can make your old life seem like a dream. You will drink too much of the locals tequilla, you will make too many friends, you will buy too many trinkets, soak in too many songs, too many cigarettes, too much romance and ritmo. You will unconciously shell out $1500 in 45 minutes without any regard for your travelers budget. You will hatch too many plots about calling up hollywood for the 'Making of a Mariachi Idol', or 'Real World Mariachi', or else you will try to devise a walk down the asile with your love in a full on 200 Mariachi salute (stay tuned for the invite my faithful readership). It is dangerous because you will wake up the next morning stiff, tired, still drunk, and cheated and think only of how to make it back there again.