Saint-Denis: As the capital, you'll find strong 4G and expanding 5G coverage across the city, especially in the city center, along the Barachois waterfront, and near Roland Garros Airport. Indoor coverage in shops and restaurants is generally reliable. The island's bus network, Car Jaune, maintains a stable connection on routes within the urban core and along the main coastal highway.

Saint-Gilles les Bains: This primary resort area has excellent network performance along the popular western beaches and in the main tourist districts. Hotels, restaurants, and bars in L'Ermitage-les-Bains and Boucan Canot have strong 4G/5G signals. You might experience slightly weaker connectivity inside large, dense concrete hotel buildings or when traveling a short distance inland from the coast.

Saint-Pierre: The major city of the south offers robust and consistent 4G/5G connectivity. The bustling waterfront, main commercial streets, and market area are particularly well-covered, ensuring reliable service for navigation and data use throughout the city's urban zones.

Cilaos: The village center of Cilaos has dependable 4G coverage, making it easy to stay connected while in town. However, mobile signal becomes very intermittent and is often completely unavailable once you venture onto the hiking trails within the Cirque de Cilaos. Expect little to no service on remote mountain paths, such as the ascent to Piton des Neiges, and in deep ravines.

Coastal Ring Road (N1/N2): Coverage is generally reliable along the main coastal routes connecting Saint-Denis, Saint-Gilles, Saint-Paul, and Saint-Pierre. However, expect signal drops in tunnels along the Route des Tamarins (N1) and on the exposed Route du Littoral between Saint-Denis and La Possession, where service can be intermittent.

Trans-Island Route (N3): When traveling between Saint-Benoît and Saint-Pierre via the N3, also known as the Route de La Plaine, connectivity is inconsistent. Signal significantly weakens or disappears completely across the high plateaus of Plaine des Cafres and Plaine des Palmistes, which separate the island's two volcanic massifs.

The Cirques: Access roads into the volcanic calderas, such as the N5 to Cilaos and the D48 to Salazie, feature highly sporadic mobile signal due to the mountainous terrain and sharp turns. Within the cirques themselves, especially in remote areas and the pedestrian-only Cirque de Mafate, you should anticipate having no service at all.

Route du Volcan and the Wild South: The drive to the Piton de la Fournaise volcano via the Route Forestière 5 (RF5) involves long stretches with no cellular signal, particularly as you ascend into the barren Plaine des Sables. Similarly, the N2 road through the less-developed "Sud Sauvage" (Wild South) between Saint-Philippe and Saint-Joseph can have patchy coverage away from towns.