Miguel is in mid-sentence when his face darkens and his eyes dart to the ground. His mouth is still open, but no words come out.
He has been talking about what it must be like to live in a country where the government doesn't control all radio and television. What he says is hardly incendiary, but when a policeman saunters by, he freezes.
"That's Cuba," he says after the officer has moved away. "They are always listening."
Saying the wrong thing too loudly in this country can cost you your job. Insulting Castro or other leaders publicly can mean jail.
Still, freedom of speech in Cuba is more nuanced than may appear. The government tolerates criticism in a few accepted spaces, and many people do express themselves in public, sometimes even loudly and bitterly -- and more so, some say, since Castro fell ill last year and his brother Raul took over.
One such relatively free space is the enclave of benches and shade trees of Havana's Central Park where Miguel was sounding off. It's called the Esquina Caliente, or "Hot Corner," from baseball lingo for third base. Here Cuban men both young and old, black and white, some with gold chains and sneakers, others in tank tops and dusty sandals -- argue sports all day, every day.
But debate sometimes spills into other areas: women, ration cards, clothes and cars. Illegal TV hookups, water shortages, booze and last night's neighborhood Communist Party meeting.
Cuba has no free press, Internet access is restricted and phones are assumed bugged. State security agents follow government critics and foreigners, while nearly every block has its "Revolutionary Defense Committee" keeping tabs on the neighbors.
So at the Hot Corner, those who deviate from sports tend to do so quietly. Miguel asked that his last name not appear in print for fear of government repercussions.
Dissident Miriam Leiva is well known enough not to mind her surname being published. She says people are encouraged to blow off steam at communist meetings -- but officials ignore what they say.
"For people to feel they are free to talk and complain, it relieves stress and allows an outlet for people to relax a bit," said Leiva, an independent journalist whose work is published on Web sites and in magazines outside Cuba. "But they express themselves because they have to, because they are suffering. Then nothing changes."
A public forum for complaining is Juventud Rebelde, the Communist Party youth newspaper.
Saily Cordero, a 23-year-old housewife, wrote saying she was being denied her entitlement to free powdered milk as a woman five months pregnant. Within hours, the neighborhood councilwoman and a host of top communists appeared at her door.
"People I had never seen around here were everywhere," Cordero said.
They checked her story and determined she was not eligible until her sixth month of pregnancy. But Cordero said the fast response made her feel empowered.
"I just want what's mine," she said. "If I don't get it, I will complain and complain. Whoever gets in trouble, I don't care."
In 1961, Castro famously defined free speech for Cubans: "Within the Revolution, everything; outside the Revolution, nothing."
"There was no other choice. It was, `you're with us or you're against us' and you can imagine what happens if you're against us," Leiva said. "That's the way things are still."