There's never any silence. Hundreds of other insomniac dancers gather at the vast backlit bar, in front of dozens of varieties of rum or vintage tequila. All tap their toes to the tropical beat, eyeing potential dance partners or homing in on their own dates. At first glance it resembles a frantic tea dance, especially since the band members all look like pensioners in frilly shirts. But the age of the clientele ranges from 15 to around 80, and every woman wears stiletto heels. It's rather like stumbling into someone's wedding reception - not an ordinary club experience. And it's impossible not to move with the music.
Dancing to salsa - which translates roughly as "saucy music"- turns out not to be completely instinctive. I have to be shown how. Middle-aged Angel, my first partner, starts off with a devilish clench, one hand gripping my waist, and gazes steadily into my eyes. Where he leads, I follow - until he starts whipping me around to the beat, sweat droplets flicking adjacent couples like stray sequins under the lights.
At all times, we must keep our hips rolling to the pulse of those bongos, cowbells or maracas that the percussionists keep hauling out, yet the upper body movements must be utterly smooth. Jerky shoulders are definitely discouraged. When a lanky Yank starts moving like a stricken chicken, the management politely but firmly asks him to leave. His offence is not upsetting decorum;, he is taking up valuablespace on the dance floor.
In Salon 21, the refurbished factory where the Cuban rhythm master El Cachao has his gig tonight, that takes some doing. The floor is bigger than a football pitch, and more than 2,000 people can salsa at the same time, even as a television crew trails after the couples with the trickiest footwork. I watch them shooting my husband steer a wiggly, boob-tubed redhead round the room, her shoulders daubed in golden glitter. When the music halts for a millisecond and they catch their breath, she smiles warmly and then slips a card in his shirt pocket.
Yes, it is her phone number, but it's not what I suspect. He is crestfallen to discover that she is a dance teacher soliciting new pupils. Soon she's back with a male instructor in pleated trousers and gold spats, who bends her back to sweep her hair on the floor for the cameras.
There's a big revival of mambo, rumba and samba going on in Mexican clubs, a parallel to the Big Band swing dance fad among teenagers north of the border for the past two years. "But this salsa is so much more compelling," Valeria gasps, flicking a feather boa to the beat. "Look around you. Some couples just never stop." A grey-haired pair, eyes only for each other, coil and twirl with obvious passion. It's half past one already, and octogenarian El Cachao is just starting to hit his stride on stage. When this session eventually ends in a couple of hours, we can always move on to Mamarumba. There, each couple must be content to pivot in place on a single floor tile because the place is packed until sun- up. Still, everyone keeps that salsa rhythm, even if they must dance with their arms high overhead because there's nowhere else to put them. Partners switch mid-melody, and the beat goes on.
Changing venues in pre-dawn Mexico City can be a little dodgy as dancers cannot trust all taxi drivers. The ubiquitous parakeet green Volkswagen Beetles can prove sinister if the face behind the wheel fails to match the licence's mugshot. Many of the taxis have been hijacked from their rightful owners, and unwitting passengers who hail them get robbed at gunpoint. Frequently, the victim is held hostage for 24 hours, just to enable maximum use of credit cards and cash machines. Two of my new acquaintances have personally experienced this highway robbery, and everyone I have met knows a recent victim.
When Valeria got a puncture last week, she didn't dare get out and change it, much less hop in a passing taxi. She ended up driving three miles home, lurching on her flat tyre, and wrecked her car's suspension. This is why, she explains sheepishly, we might eventually have to take a taxi tonight, although she swears she has the number of a trustworthy local cabbie somewhere in the bottom of her purse. It puts a certain edge on the evening. We feel we have to seize the night before it seizes us. Salsa anyone?