First Time Solo Traveling & First Time in Costa Rica: Looking for Tips

I will be taking my first solo trip (F, 26) to Costa Rica at the end of December. Equal parts nervous and excited. Will be staying in Atenas region first few days & last few in Jaco, all in AirBnBs.

First AirBnB family offered for me to rent their car. Heard the roads/driving in Costa Rica aren't the best, but want the freedom to go wherever I please. Thoughts?

Also looking for good companies and/or tips for guided tours/must-see-spots in both Atenas and Jaco.

Any and all recommendations/expertise welcome :)