Where to shop for cars:

The English sources generally have the highest prices.  Try:

www.craigslist.org - This is very popular in the states and just started here last year.  It looks like it will be a good source for cars.
www.amcostarica.com - This is a daily online English newspaper.
www.ticotimes.net - This a weekly online English newspaper.
www.insidecostarica.com - Another daily English newspaper but their ad section is very limited.

The Spanish sources have the most variety. Listed in my order of preference are:

www.crautos.com - By far the largest selection of cars on line.
www.nacion.com - Spanish daily newspaper.  Tuesday is the “Auto” day.
www.telatica.com - The local channel 7 TV station. They have a ways to go.

Panama - For the not so faint of heart
I am planning on making a trip to the border of Panamá to buy a Toyota possibly a Toyatona or Prado turbo-diesel SUV.  The expected price with all import taxes is $18,000 - $20,000. The same car already inside Costa Rica is currently selling for $24,000 and up.  Why the price difference? People don’t understand the process or buying from Panamá and it is a real pain to go to the border.  But you need to be careful - a lot of the cars for sale in Panamá have been stolen and have forged documents. Make sure you know what you are doing otherwise you may loose everything!