Depends on the length of your Trip, but if your time is limited then 2 days in Monteverde will be enough. One day you can spend in the Moneverde preserve and next day you can do canopy tour and sky walk since they are next to each other and the road is horrible - you don't want to go to this direction twice!!! You will still have time to visit Snakes, Butterflies, and frog exhibitions if you are interested. For Arenal, one day is enough to see the volcano. You gotta see its erruption over night though - it is amazing.

Take enough time for travelling. Some friends and I took the route San Jose, Alajuela, Sarchi, Zarcero, Fortuna, Arenal, Tilaran, Monteverde. Roads are bad and they get worse as you approach Monteverde. Last 25 km are bumpy gravel road.

When you are done with Monteverde, you continue your trip south from Santa Elena towards Puntarenas. Same here, first 25km are gravel, it gets better and faster later.

From Puntarenas to Jaco it is a highway and you are there in less than 1 1/2 hours. Make sure you stop at the Tarcoles bridge to see the crocodiles.