If you wish to work in the country or to enter education you will need to acquire a special permit which allows you to do so. Authenticated documents will be needed for this permit, for example photographs, police good-conduct reports and certificates of good health. You can apply for these permits from Salvadorian embassies before you travel or in the country itself.
To work in the country you need to apply for Temporary Residence with Authorisation to Work, applications for which need to be made directly to the Immigration Department. There are certain requirements which will need to be fulfilled and documents they will need to see, for more information see the employment authorisation section ofpubweb.fdbl.com.
The Centro de Intercambio y Solidaridad is often looking for bi-lingual project managers and liasons to hire, and they offer Spanish classes and other cultural and volunteer opportunities.