For out Costa Rica trip we are not really planning to rent a car. We wil be getting from San Jose to Arenal with the rafting company. From Arenal to Monteverde we are thinking of booking car-boat-car transfer and from Monteverde to Montezuma we will proably go with the private transfer then includes car and ferry. It is 4 of us so it looks like not a bad deal.
But I a not sure if we should rent a car for our stay in Arenal. We will be staying for 4 nights, 3 full days in Spring Spa resort and planning to do some hiking, canyoning, hanging bridges, either hike or horseback riding to waterfalls...We would want to go somewhere for a dinner. Is it easier to get around by hiring taxis? Are they easy to find? How far are all attractions from each other? Would it be easier if we have a car? Appreciate any info and recommendations

We were in Arenal a couple years ago (stayed at the Lost Iguana), and we did not have a car – we did not find that to be a problem. All tours picked us up from the hotel, and taxis were easy to find, just ask your hotel.
If we ever go back to CR (actually, WHEN we go back to CR) we’ll not get a car, it’s really easy to get around without. Enjoy your time there, you’ll love it.

We never rent a car because we do so many tours, and they'll usually pick you up and drop you back at your hotel. A lot of people do like to have one though because things are spread out. We just take taxis and have never had a problem asking either the hotel or restaurant to call one for us. They come pretty quickly; they also congregate around the park in the middle of town. So you don't really need one, but it makes it a little more convenient to have one.

Yes, I agree with the other posters that you won't need a car in Arenal. I actually stayed in the town of La Fortuna (the town at the base of the volcano) and my friends and I were able to get around the area through the tours we had signed up for picking us up and taxis (which are plentiful and easily called for by hotels, etc). We even hiked up from the town to La Catarata (the famous waterfall there) and that was a hike but doable.

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Many thanks for yor advice. I am happy to know that we do not need a car. Makes our life planning easier