The San Luis Rey River Trail is a paved and unpaved multi-use path that follows the river from the ocean at Oceanside Harbor inland through riparian woodland and coastal sage scrub. The lower reaches near the harbour and estuary are particularly good for birdwatching — herons, egrets, and migratory shorebirds gather in the river mouth, and the riparian corridor supports a wide variety of songbirds.
The trail extends well inland from the coast, offering options for walks of different lengths. The river mouth itself, where fresh water meets the Pacific, is worth visiting on its own — a narrow inlet between sand dunes that feels surprisingly wild for a city setting.