A light-skinned Mexican wearing casual work clothes with a tie around his neck stands in the trolley with a black backpack. He looks around to make sure there are no security guards watching him. Then he walks through the car and in a loud whisper asks, “Queso monterrey? Queso cheddar?" Several trolley riders stop the cheese seller and buy a one-pound block for $5.

That was the first time I saw a vendor in a trolley, more than a year ago. I didn't give it much thought; unlicensed vendors in Mexico are everywhere. It wasn’t until I saw a tall black guy with a shaved head and an older white man covered in tattoos also selling cheese that my curiosity arose. Especially because I have seen the black guy in the Caliente Casino, most likely gambling the money he makes from selling cheese.

“Yes, we are more than aware about the illegal vendors,” a trolley security guard told me on September 4. “I don't know how much they get fined — I just write the citation and the court handles the case. In fact, I really want to know what they charge them. I've seen repeat offenders and I ask, but they won't tell me. They think I am trying to get them in more trouble.”

I interviewed several officers and they all knew about the illegal queso. Besides cheese, other popular items for trolley vendors are chocolate, granola bars, and other types of grocery items that can be quickly sold. The vendors usually get on at Palomar Street and get off on the last trolley stop in San Ysidro.

“There is no doubt that they purchase the food with food stamps,” said an officer at the San Ysidro stop. “I have also caught people selling watches and perfumes, most likely stolen ones.”

I ask if he knows the black vendor.

“The tall black guy with a shaved head? Yeah, I know who you are talking about. The problem is that we have to catch them in the act or we cannot write a citation. There's cameras in the trolley, you know? We are aware of who they are and I have spoken to my boss about taking more action to solve the problem, but in the meantime we can only ticket them if we see them selling.

“Besides him, there are single mothers with their children selling all sorts of groceries. We have the option of confiscating the items that are being sold, but when mothers with children are trying to make cash illegally, I usually tell them to move along or they can get in big trouble. I don't want to take away food from a whole family.”

As for why queso is the most popular item, trolley security does not know.

“I guess they need the cheese to put in their quesadillas and stuff. Why buy it in the trolley? They might be saving a dollar or two, but I don't really know why cheese is the most popular item.”

From personal experience and as an extreme queso lover, cheese in Tijuana supermarkets is either cheap and horrible or expensive and of mediocre quality. To find decent cheese at a good price, you have to go to quaint mercados that usually close early. I asked several queso customers why they would buy from a stranger on the trolley. They all had the same answer: “Porque esta bueno y barato” (because it's good and cheap).