Popoyo is roughly two hours south of Managua by road. Take the Pan-American Highway south to Rivas, then head west toward Tola. From Tola, a paved road leads to the coast — follow signs for Popoyo or Guasacate. A taxi from Rivas to Popoyo costs around $20–30.
There is no reliable public transport directly to Popoyo. The most practical option from Managua is to rent a car or take a taxi-share (colectivo) to Tola and arrange a taxi from there for the final stretch. From Granada, the drive is about 90 minutes via Rivas.
San Juan del Sur is about an hour south along the coast and better connected — if arriving by long-distance bus, consider stopping there and arranging onward transport.