Costa Rica may be almost first world in some areas but don't expect that in the roads or drivers. The ccountry has made a decision to focus their budget on healthcare and education and so sometimes roads can be awful and signage confusing.
Luckily there are excellent and very affordable options if you don't want to rent a car and drive yourself including:
An excellent and very affordable public bus network. Prices are generally $5-$10 for a one-way trip anywhere in the country. Some routes have both local and express buses so make sure you get the express route not the "milk run". This document from the Costa Rica tourism board gives the schedules for every bus route in the country. For many routes, advance tickets are highly recommended. For many destination, our transport planner offers a service which includes pickup at the airport or your San Jose hotel and advance ticket purchase if you're not able to get to the bus station a day ahead.
A system of tourist shuttles run by several companies such as Interbus and Grayline that offer door-to-door service from most hotels in major tourist locations. Check out the transport planner for routes, schedules and rates.
The option of hiring a car and driver can be quite affordable in Costa Rica and can take all the stress out of driving. It is also sometimes the only way to safely maximize your vacation if you want to head directly to the beach from your airport arrival as many destinations to not have scheduled transport after a certain hour. The transport planner has fixed point-to-point rates for many popular routes.
Two airlines, Nature Air and Sansa, run regularly scheduled turbo-prop service between San Jose and destinations all over the country. With prices generally running $40 - $100 oneway for a 30 to 75 minute trip it's a great way to maximize your vacation time. Check their websites for schedules and prices.
Many tour packages include transport and also sometimes include the option to be picked up in one location at the beginning of the day and dropped off elsewhere at the end of the day. Not only do you get your transport for free but you don't end up spending what feels like a wasted day just in transit. For example, the Pacuare River Whitewater Rafting trip includes pickup and dropoff in your choice of San Jose, Arenal or the Caribbean. Contact our travel partner, Gecko Trail Adventures, for advice on the most efficient and fun way to get to your destination.
If you do want to drive, then all the major rental car company companies have offices in San Jose both at the airport and in the city. There are offices of many of the companies sprinkled around other locations as well.
We don't recommend that you drive unfamiliar routes after dark. Signage can be poor and potholes and other road hazards can be very unexpected.