for hotels , check the Sponsor list, and then check the Map to see where they are. But no matter what call to make a reservation. The sponsor's are not huge operations, like a US Chain motel, so they can fill up fast. I you plot SL and DR on the map, you can locate the hotels in relation to those twp places and then every thing falls into place. And make sure you take a couple copies of the map with you.
On this short a trip the drive might be pushing it, you do not travel distance as easily on CR as the US.I found driving in CR is far more tiring then in the US. By the time you wake up Sunday( and that can be a great variable depending on how many times you all in love SAT night ),sober up??, get a car, drive to Jaco, a whole day can be shot, then to repeat it the next day back could be a question of endurance not fun. Add a couple of days maybe, but for over night IMHO a little to much.
Suggest maybe stay in SJ for the first trip and explore one area
But if you do rent a car, Make the return hotel reservation before you leave for Jaco ( save time on return looking for a room) and if you rent a car, takes some photos of the car with the rental agent in a few of them just in case there is any question about damage when you return, saved my but on one rental )