I didn't but I'm thinking that you're likely going to be a bit better off on American, Delta or Continental directly into San Jose. But I'd also check out what airlines you can catch into Liberia in the northwest part of the country. When I go back, I'll avoid SJ all together and go straight into Liberia. But flights there aren't as frequent as Juan Santamaria. (The airport is actually in Alajuela, which is about 15-20 minutes from San Jose Central.)
Have you checked www.mobissimo.com?
It searches all the airlines, and the Travelocity-type sites.
Also, Mexicana IIRC codeshares with TACA who flies all over Central and South America.