Natural hot springs is very popular in La Fortuna/Arenal. The most popular tourist hot springs is Tabacon but it's very expensive. For $80 per person you can enjoy the hot springs inside Tabacon and it comes with a buffet dinner. You can also go there for lunch and it's a little bit cheaper.
For a cheaper alternative, we were told to go to Baldi hot springs. It offers the same hot springs and buffet combo for lesser price than Tabacon.
We opted for neither of those places and instead asked our trusted hotel receptionist, Rebecca to give us the name of a local hot springs she would go to. She told us to go to Termales Los Laureles. It was a 10 minute drive from our hotel and we absolutely loved it.
For $12 a person, you can't go wrong with the price plus we loved the fact that it was mostly locals who go there. No overcrowding either.
Not only do they have the hot springs, you can also use the different pools that they have.
The grounds are well kept aside from a minor construction for the slides.
The hot springs has 5 different tiers. The top is the hottest and it goes down in temperature as you go to the lowest tier.
The attractions in Arenal and La Fortuna closes before 5pm and nothing else to do at night but to eat out. This is a great way to spend some time outdoors while enjoying the natural hot springs from the volcano. I soaked here for hours.
Change room facilities are available and I believe you can also use a locker but you have to bring your own lock.
You can also bring your own food and have a picnic. Benches and tables are provided including a barbeque station. Just be sure to bring your own charcoal and grilling equipment. You can spend the whole day here with family and friends.
We actually came here twice. On our second night, we brought our own food and had our dinner in one of the picnic huts. It was the best!