You are given a sniper rifle by Auntie Poulet. Follow the blip in the radar to the roof of a building nearby. The roof can be accessed by a staircase on the back side of the building. An adrenaline pill is located beneath the staircase, useful when sniping the Cubans.
Snipe any Cubans in the area. Do not be spotted by the Cubans and do not attack the Cubans with other weapons. At least one Haitian has to remain alive to pass the mission. The Cubans will bring reinforcements and weapons to try to win the battle.
An alternative strategy is to use the revolver to eliminate the nearer Cubans swiftly; in the PS2 version at least you will not be spotted provided you remain in the start location. This is especially effective at killing the second wave of reinforcements. You will still need the sniper rifle for Cubans further away, so quick weapon switching is essential.