San Juan del Sur sits 140 km south of Managua and about 30 km south of Rivas, the nearest substantial town. There is no train service; all travel is by road.
From Managua, express minibuses run frequently from the Mercado Huembes terminal (around US$3–4, two to two-and-a-half hours). Chicken buses are slower and cheaper. Alternatively, take any bus or minibus toward Rivas and change there — frequent services run from Rivas to San Juan del Sur (30 minutes, less than a dollar). Taxis from Rivas cost around US$15–20 and can be a sensible option with luggage.
If crossing from Costa Rica, the nearest border post is Peñas Blancas, about 45 km south. Minibuses connect the border to Rivas, and onward transport to San Juan del Sur is straightforward. Shuttle buses marketed to tourists run the Managua–San Juan del Sur and San José–San Juan del Sur routes and are more comfortable if more expensive than local transport.