Heredia's city centre is compact and walkable — the main sights around the Parque Central are within a few minutes of each other on foot, and the National University campus is a short walk east of the park.
For reaching the surrounding hills, the most practical option is a rental car or a taxi. Taxis are plentiful in the city centre and affordable. Buses connect Heredia to nearby towns including Barva, Santo Domingo, and the outlying villages, but schedules can be infrequent for the more rural destinations — check locally before relying on a bus to the Barva volcano trailhead.
Rideshare apps available in Costa Rica work well in Heredia and are a useful fallback when taxis are not immediately available. The city is flat and navigable, and most travellers find they need a vehicle only for excursions into the hills.