The barmaid rolled her eyes and said: 'They play that day and night. The thump of reggaeton boomed loudly from cars passing Bodega Chic. Calle Cristo runs from the top like a colourful ribbon, almost all the way to the bottom, framed with pink flowers and vividly painted houses. I started at the top by San Juan Wall, high above the seafront. America's efficient infrastructure is a boon rather than a curse, and there are still plenty of old haunts – from traditional shacks to polished bars – that are well worth a visit. Sitting on the island's Atlantic coast, at the foot of the Cordillera mountain range, San Juan these days gives an impression of well-behaved hedonism, with a mixture of African, European and Taino Indian cultures. The city is a lot less troubled, for starters. Set in the early 1950s – a few years after the US decided to make Puerto Rico an unincorporated dependent territory – the book shows, through Kemp's eyes, a volatile yet fun-loving Old San Juan. Also starring, in all their Technicolor glory, will be the old town's pretty bright blue, orange, pink and purple neo-classical houses set on steep hills, as well as its traditional bars and dusty cafes with ancient waiters. The film of Thompson's book – which is mainly based in Old San Juan but also takes in the Condado and Isla Verde areas – will be released this year, starring Johnny Depp as Kemp. Scene from The Rum Diary, starring Johnny Depp. Far away from the SUVs and shopping malls now common on the island, this is Old San Juan, the Unesco-protected old quarter, where the roads are so narrow that anything bigger than a Chevrolet would struggle to squeeze through. Bacardi – probably straight from the distillery a short ferry ride away – was sloshed into a glass and served with fresh mint and soda water. As I sat on a stool in Bodega Chic (+1 7) on Calle Cristo, the bohemian spirit of the 1950s and 1960s fluttered around me, with framed old newspapers and yellowing bar tabs clipped to an old washing line. My bodega of choice wasn't as insalubrious as Kemp's (fictional) haunt – a makeshift bar called Al's Backyard – but it was traditional enough to quell rumblings that San Juan is turning into a bastardised version of Miami.

So far, so Paul Kemp – the protagonist from Hunter S Thompson's book The Rum Diary who spends most of his time in tiny sweaty bodegas knocking back the finest fermented molasses the city has to offer.

Whether it is the lazy fan circling overhead, the warm breeze primed with sea air or the background fuzz of Spanish songs on a crackly radio, it all distils into the perfect atmosphere. T here is something about Old San Juan that makes drinking rum at 11am seem a perfectly acceptable activity.

The Rum Diary by Hunter S. Thompson