The Latin American presence in Ann Arbor shows itself only in intermittent signs — a Spanish-language church service here, a section of Mexican groceries there. For Ann Arborites who travel around the country a bit and have witnessed the explosive growth of Latino populations in formerly black-and-white Charlotte, in corn-country Des Moines, and just about everywhere else, the lack of a Spanish-language streetscape in our hometown can seem vaguely unreal. But our turn will no doubt come. In the meantime, if you want a glimpse of the future, check out Mexican Night on Sundays at the Heidelberg’s Club Above.

Around 10:30 p.m. things are quiet. But wait until midnight, Raymond, the Heidelberg’s owner, tells me — everybody gets off work at 11, goes home and takes a shower, and then comes in. Sure enough, by midnight the place is filled with young men, some of them in cowboy hats, and women looking more formal in black pants and white shirts. Some come to mix and meet, but some are there to seriously dance, to whirl around the room when the lickety-split merengue, with its nimble saxophone lines, sounds from the bandstand. If you want to get in on the action yourself, flyers on the bulletin board at the door advertise Latin dance lessons.

Ann Arbor may be a small town in Mexican American terms, but tonight an ensemble from Chicago, Grupo Explosión, takes the stage. These musicians are terrific. They do a little of everything, says the woman in a stars-and-stripes scarf who takes my money — salsa, merengue, cumbia. This is a big group for such a small room, and its members switch off among the instruments that give each of these national dances its particular flavor. (Salsa is Cuban and Puerto Rican, cumbia is Colombian, and merengue is from the Dominican Republic, but all find a place in Mexican American music these days.) The group also plays pieces that sound a bit like old American rock ‘n’ roll, and during the breaks a DJ spins the old-style polkas and rancheras that still dominate the dance halls of northern Mexico. What with all the musical mixture, I think there’s some overlap in the crowd between Mexican Night and the Heidelberg’s other Latin dance night, on Fridays.

So go to listen — the range of Mexican and Mexican American music these days is an exciting thing and a reflection of the incredible variety of influences at work in the culture from which they spring. Go to dance. Go to talk — it’s a friendly crowd. And go just for the sake of being curious, because before too long there may well be half a dozen Mexican dance nights in our until now Latin-deprived county.