Chiclayo itself is navigable on foot or by mototaxi (the three-wheeled motorcycle taxis that swarm the city). For the archaeological sites outside the city — Sipán, Lambayeque, Ventarrón, Ferreñafe — you have three options: hire a taxi for the day (negotiate a price in the morning), take a group tour from one of the agencies on the main drag near the Plaza de Armas, or piece together the journey using the frequent combi minibuses that run between Chiclayo and Lambayeque.
The buses and combis to Lambayeque (for the Brüning Museum and Royal Tombs Museum) leave from near the Mercado Modelo and cost almost nothing; the journey takes about 20 minutes. The sites further afield — Huaca Rajada at Sipán, Ferreñafe — really need a taxi or organised transport.