Three walking reserves share the mountain, plus two bridge parks in the canopy. You do not need all five. Here's the honest sorting.
Monteverde Cloud Forest Preserve
The original and the famous one, run by the Tropical Science Center. The most dramatic old-growth cloud forest of the three, the continental divide trail, and the biggest crowds by mid-morning. Tickets are sold online per trail/time at the official site — don't plan on winging it at the gate. Foreign adult entry runs about $29; check the official page for current rates and kids' pricing. The visitor center sits about 1.5 km below the entrance with a shuttle up.
Pick it if: it's your one cloud-forest day and you want the canonical experience. Go at opening.
Santa Elena Cloud Forest Reserve
Community-run, quieter, slightly higher and mistier, with views toward Arenal on clear moments. No advance reservation needed for individuals — capacity limits rarely bite outside absolute peak weeks. Adult entry is in the $18–21 range (students and kids less; sources differ, the gate wins).
Pick it if: you want the same forest with half the people, or the Monteverde preserve's slots are gone.
Curi-Cancha Reserve
Half forest, half open former-farmland — which is exactly why birders love it: more light, more edges, and the best resplendent-quetzal odds on the mountain (roughly December–May for nesting season). Entry reported between $20–25 for adults depending on source and season; guided birding, natural-history, and night tours available.
Pick it if: the quetzal is the mission, or you're carrying binoculars and mean it.
The hanging bridges
Bridge parks put you in the canopy without the climb — a different (and more photogenic) experience than the reserves, worth it even if you also walk a reserve.
Selvatura Park — Treetop Walkways
Eight bridges over ~3 km of trail, the longest at 157 meters. Self-guided runs about $43 adult ($30 kids 4–12), guided more. Big operation with ziplines and other add-ons if that's your crowd.
Sky Walk (Treetopia Park)
Six bridges on a two-loop circuit — the former Sky Adventures park, recently rebranded Treetopia. Self-guided around $38 adult, $27 kids 5–12. Usually the slightly cheaper, slightly quieter bridge option.