After leaving work, he heads there and buys the 10 grams that Uruguayan law permits, costing 400 pesos, around US$13. Fernández then heads home and rolls a joint "to relax" with his partner Stefania Fabricio.
No longer do they need to surreptitiously contact a dealer and pay more for Paraguayan or Brazilian marijuana that's been "pressed, mixed [and is] sometimes very bad and full of chemicals."
"Now it's much easier than when it started," Fernández, a 31-year-old who works for a cleaning company, told AFP.
She says she feels "privileged" to live in a country that enacted a law to "get tons of people out of the black market." As a result, she said, the stigma attached to those who smoke pot is changing, "albeit slowly."
The system is simple: to buy cannabis in a pharmacy you must be at least 18, live in Uruguay and sign up as a "buyer" at the post office.
An initial stumbling block arose when banks refused to work with establishments selling cannabis due to international rules against drug-trafficking. But the country plowed on, and last year it became the first in the world to fully legalise its sale.
Users can choose between two brands and two types of cannabis – sativa and indica – both provided by an official distributor.
Customers are generally not the stereotypical grubby-looking student or idle waster. On this day in Curbelo's store they include two young women, a man in his 50s and an older lady – "normal people," says the pharmacist.
Official statistics say 70 percent of buyers are male and 49 percent are between the ages of 18 and 29.To keep anyone from exceeding their monthly allowance, a fingerprint machine is used to register every sale.
Along with the ability to purchase cannabis in a pharmacy, Uruguayans have the right to grow their own – up to a six-plant maximum – or to join a cannabis club, which can have up to 45 members and 99 plants.
Federico Corbo, a 41-year-old gardener, grows cannabis in his garden on the outskirts of Montevideo. He experiments by crossing species in an attempt to improve quality and optimize the flowering period. Corbo is not impressed with the quality on offer in pharmacies.
"It's not the worst, but it's low," he said, insisting quality control needs to be improved.
"Marijuana that doesn't reach the minimum standards – with crushed flowers, no aroma, low quality – shouldn't be sold in the pharmacy. Maybe, as I'm a grower, I'm very demanding, but there is a cost associated to the product and it must be offered to the public in the best way possible."
According to the Institute of Cannabis Regulation and Control (Ircca), an average cultivator or club member supplies cannabis to two other people, while those who buy it in a pharmacy share it with one other.
"Approximately half of marijuana users have access to regulated cannabis," says Ircca.
The rest prefer to continue buying the drug on the black market, put off by the need to register as a user.
"It's wrong – if they legalise it they have to do so in a way in which the state doesn't keep a paternalistic role in overseeing how much you smoke or stop smoking," one clandestine user, who wished to remain anonymous, told AFP.
This 48-year-old lawyer simply doesn't trust the authorities. He pointed to the danger a change of government could bring, or even the return of dictatorship.
"Right now that seems impossible," he said, "but you can never discount it."