If they're capable of 1950s era urbanism, they're capable of 1950s era agricultural technology. They get enough dollars from tourism and exports to purchase make up for what they don't have just like any other small nation. The are perfectly capable of growing tobacco and sugar. The problem is that the profit from non-cash crops is either too low like staple carbohydrates, or too variable, like fruits and vegetables to incentive farmers in a socialist country.