Finding work/Volunteering/Improving my Spanish (San José)

Hi there,
I'm studying Spanish in the University of Limerick, in Ireland and as part of my degree, it's compulsory to work abroad in a Spanish speaking country. I'm seriously considering Costa Rica but I don't have the foggiest of ideas about how to go about this.. I'd love to start in January and work for 6 moths or so. Any advice would be much appreciated as I don't know where to begin..
Warm regards,
Pat