Yo, Amigos:
I have spent a good bit of time in CR. I have a secret weapon. It is called "Costa Rica by Bus." It is a great little book, written by John R. Wood, retired IBM engineer and father of Chris Wood, who lived in Guadelupe and who used to own the Nashville South Bar, on the west side of Parque Morazon, a couple of blocks from the HDR.
There are a large number of bus companies in CR. Most have one or two routes. John has collected all the information on virtually every route: local city routes in San Jose, longer cross-country routes, and international routes for trips to Nicaragua, Panama, etc. On my first trip to CR, in January of 2006, my wingman wanted to hire the airport taxi driver to take us to Jaco a few days later. Dude quoted us $80 or $100. I waited to check out the Tico bus and found a nice bus, with assigned seats and tickets could be purchased ahead of time, for $2.50. When I made the trip to Jaco last year, the price had gone up to $4.00 or so. Since then, I have traveled all over CR by bus, and the most I ever paid for the longest trip (Golfito) was about $6.
There are two Buslines providing transportation between downtown San Jose and the airport, Station Wagon Alajuela (red) and Tuasa (yellow). The buses run about every 10 minutes during the day. I have never tried to find one late at night, but Wood says they run every 30 minutes after 11 p.m. Their stations in San Jose are a block apart, on Avenida Secunda, near the Mercado Central, a block from Avenida Central, and walking distance, if one is traveling light, from the HDR. Each company has two routes, either clock-wise or counter clock-wise. One bus leaves San Jose headed first to downtown Alajuela, then to the airport, then back to downtown San Jose. Another bus leaves about the same time headed first to the airport, then to Alajuela, then back to San Jose. So, it is important to inquire of the driver whether he is headed first to the airport or Alajuela or San Jose vs. Alejuela, depending on which way one is headed. The last time I rode the bus from downtown to the airport, last September, it was about 400-450 colones, less than 1$. Upon arrival in San Jose, taxis are plentiful on Second Avenue. The bus stop in front of the airport is very easy to find. I agree with other posters who recommend that, after clearing customs and baggage claim, one should go upstairs to the departure area and do two things: pay your departure tax and convert some $ at the bank right beside the departure tax desk. Then, just walk out the front of the airport, turn left, and walk down to the street in front of the airport parking lot. The bus stop is easy to find. There are usually some Ticos waiting for a bus, and when real busy the bus company sometimes has a guide to get folks on the right bus.
John Wood's book is published by Bookstand Publishing. There is a website for it,
www.costaricabybus.com. I never leave home without it.