Hi, Dani - guessing from this Cursillo link, the religious verses came later. However, it appears that the song may have been popular in Cursillo first, and then moved to popularity in the United Farm Workers movement. I was involved in a youth program related to Cursillo in the 1960's - I learned the standard two verses, but not the religious ones. I didn't come across the religious verses until dwditty posted them here yesterday.
Curillo, by the way, is an ecumenical movement that finds a home in the so-called "mainstream" churches. Cursillistas can often be found in movements that work for social justice. I don't know of any connection between Cursillo and Evangelical Christianity - it seems to be more for the "liberal" side of Christianity. I've been quite impressed with Cursillo. Heck, it can even get Episcopalians to show a little emotion....
(grin)
-Joe Offer-