The Monteverde Arenal route is a little longer than the direct route of the crow. As the crow flies,
it's about 15-km (10 mi) from Monteverde to Arenal but the road, by car, is considerably longer. It's over 130-km (85 mi) by
road. This probably isn't a long trip in the U.S. but it sure is a different trip in the cloud forest mountains of Costa Rica.
If you rent a car or 4WD/SUV, you'll need to drive from La Fortuna to Tilaran; the road is in good condition. But, from
Tilaran to Monteverde it is bumpy. I'm sure, at one point, that I was walking faster than my lil' rental (SUV) was driving. The dust
was unpleasant but I needed a break from the bumps. Most people fly into San Jose and then head to Arenal and to Monteverde.
I did the trip from Liberia so I went to Monteverde and then to Arenal. Either option works.
You'll definitely need a SUV during rainy season, if you want to make this trip, but during dry season it might be possible
to make it in a car. My only concern with SUV rentals is that they are so heavily rented that the tires are in poor condition.
Read the rental contract about tire coverage. I noticed that the rental car tires were in far better condition. So, I'm not sure
that the marginally higher clearance of my small SUV was so much of an advantage, especially if I had to sit and wait
for a tire repair in some small center in Costa Rica because the tires of the SUV didn't hold out. We still had to drive at angles across
the big potholes in the road even in the SUV. I imagine that the car would have made it using the same strategy.