A lot of people think Monteverde is a lot of wildlife, but its a Cloudforest and high elevation, so it has a plethora of fauna, and birds, but thats about it, and that time year would be very misty/rainy and foggy.
You can not really go as a day trip, it is 3-4 hours drive from anywhere, and 3-4 hours drive back. The last hour is a rutted slow go mountain road, odds are it will be raining and hard to see.
The Top Parks and regions for wildlife, nature and Bio Diversity are-
Corcovado-Osa (Southern Zone 9 hours from San Jose) best to fly in out, and best for hiking.
Tortuguero
Sarapiqui-La Selva
Cano Negro
Cahuita
La Amistad-Chirrrpo
Cano Negro a nice place with a pool, as its hot, and cafe, as there is not much of a town. This place is lovely and relaxing too. Do a boat tour in morning first thing, as it gets hot. 1 night is fine.
Animal activity is best from twilight to 11...for the entire country, then it shuts down, so early rising and off to see the nature is the rule of thumb.
https://hoteldecampo.com/
For Tortuguero, best to stay in the village, they you can access the guides, boats and enjoy the towns cafes and mom & pop feel, the village is all foot paths, no roads. Everyone knows everyone. I like to stay by the soccer field nearer the ocean, its peaceful, about 500 meters from the village/docks/boats. I stay at Mis Miriam II, basic and fine. Ceheck Trip Advisor, Booking.com or AirBNB. If you stay a lodge off the river elsewhere, nice but you are isolated and have to use the boats for everything, and that gets $$$.
In Cahuita, I love the Alby Lodge. Thatched roof bungelows, monkeys and sloths everywhere. Share kitchen, old school town and with great seafood, and afro caribe spice dishes.
South of Pt Viejo, I like Playa Cochles, Chequita and the paradise of Pun ta Uva. Rent bikes and slow down and chill. PV the town is a great foodie/cafe and hang out for nightlife on the chilling vibe side. Sat night maybe a disco open till 12am...depends on time of year and how busy.
Sarapiqui La Selva, a must, try to stay at lodge so you can use the 30 miles of trails 24/7, this is a major world reknown park for tropical studies, all guides are research scientist from around the globe and major universities.
If not lodges around area, or try the Treehouse Posada Andrea-Christina
Use Booking.com or AirBNB/VRBO.
Let me know what you need, been going to CR and this coast for years...