Yes, it is doable on buses
Costa Rica has a reputation as the country that eats backpacker budgets, and it can — but the classic volcano-cloud forest-Pacific loop works fine on public buses and one famous boat crossing, and camping or dorm beds keep it sane. Two weeks, no rental car, roughly US$55-75 a day.
San José, 1 day
Nobody comes for San José, but give it an afternoon: the gilded National Theatre, a casado lunch (rice, beans, plantain, protein, about 4,500-6,000 colones) at the Central Market, and an early night. Direct buses to La Fortuna leave from Terminal 7-10 (about 4.5 hours, around 5,500 colones).
La Fortuna, 3 days
La Fortuna sits under the near-perfect cone of Arenal, which last erupted in 2010 and now steams politely instead. The town is touristy but earns it. Hike the 1968 lava-flow trails at the volcano's base (park entry about US$18) or the Arenal Observatory grounds for coati sightings and the best head-on volcano views. The free hot river is real: locals and travellers soak in the thermally heated stream that runs under the road near Tabacón, warm as a bath, no ticket required — bring sandals for the rocks and nothing you would mind losing. Splurge option: La Fortuna waterfall (US$20), a 70-metre column into a swimmable jade pool at the bottom of 500 steps. Dorms run US$15-22.
The jeep-boat-jeep
Monteverde is 25 km from La Fortuna as the toucan flies and five hours by road around Lake Arenal, which is why everyone takes the jeep-boat-jeep transfer (really van-boat-van, about US$30-35, book at any hostel): a van to the lakeshore, a launch across Lake Arenal with the volcano shrinking behind you, and a van winding up the washboard road into the Tilarán mountains. It is half transfer, half scenic tour, and the temperature drops ten degrees by the top.
Monteverde, 3 days
Santa Elena is the town; the cloud forests are up the hill. The Monteverde Cloud Forest Reserve (about US$25) is the famous one — go at opening, hire a guide or shamelessly shadow groups near the entrance, and you have a real chance at a resplendent quetzal between roughly January and July, a bird so absurdly plumed it seems designed by committee. The Santa Elena Reserve (about US$18) is quieter and mossier. Do one adrenaline thing — the long ziplines or the hanging bridges (US$45-60) — and one night walk (about US$30), when the forest switches shifts: sloths, kinkajous, tarantulas in doorways of their burrows, and clouds blowing through your headlamp beam. Nights are genuinely cold; pack a fleece.
Down to the Pacific: Manuel Antonio, 3 days
Buses run from Santa Elena to Puntarenas (about 2.5 hours), then along the coast to Quepos (2 hours more, total about 6,000-7,000 colones), gateway to Manuel Antonio. The national park (about US$18, closed Tuesdays, book online) is small and perfect: sloths draped in the almond trees, capuchins running extortion rackets at the beaches, and Playa Manuel Antonio itself, a white arc inside the forest. Guard your bags — the raccoons and monkeys are professionals. Stay up the hill in Quepos for cheaper beds (dorms US$14-20).
Uvita and out, 2 days
An hour further south by bus (about 2,500 colones), Uvita is mellower: the Marino Ballena park's sandbar, shaped uncannily like a whale's tail, uncovers at low tide (entry about US$7), and humpbacks calve offshore July-October and December-March — some of the most reliable whale watching anywhere (boat tours about US$50-60).
When to go
December to April is dry season on the Pacific; May, June and November are green, cheaper and still mostly sunny mornings. Buses are safe and cheap; just never leave bags in overhead racks unattended. Pura vida is a customer-service slogan right up until a sloth crosses the road in front of your bus, and then it is simply true.
