www.CostaRicaTicas.com

cheapest I've seen in a while 380$ including tax,ewr 480,same time frame,jan to mar.

I paid $330 through USAir for my October trip from Boston. When I got stuck down there during the hurricane they switched me to a Delta flight the following day for free. I heard numerous stories from AA flyers about having to buy new tickets or being stuck without any notice.

I found it on yahoo travel for 304 before taxes after 369.04. This is my secret trick but, i'm sure this isn't a secret . It seems that your dates are pretty flexible. So go to yahoo travel punch in EWR to SJO choose the option that "My dates are flexible" and search. I am getting a fare for 304 right now as we speak. It might change tomorrow but, for now its 304 but, after taxes and surcharges its
$370. Also don't knock AA i havn't experienced any problems with them lately. Usually they have the lowest fare but, of course YMMV. I'm a member to AA ff and I have problems with it of yet.