I have always abhorred the trite bumpersticker philosophy "Preach the Gospel, if necessary use words". For one thing it's wrong theologically, historically, and spiritually. To me it's always seemed a bit rude and arrogant claiming that those who "practice the Gospel" are more faithful than those who verbally preach it. I know atheists who live a life such that you wouldn't know they do not believe God until they opened their mouths.
As for Francis, he never said such a thing, nor did he follow such unbiblical teaching. Mark Galli, senior managing editor at Christianity Today, wrote an article on this false quote (as well as a biography on Francis) He explains that Francis was quite a preacher, actually more along the lines of Jonathan Edwards or Billy Sunday:
His words were neither hollow nor ridiculous, but filled with the power of the Holy Spirit, penetrating the marrow of the heart, so that listeners were turned to great amazement.
Francis pent a great deal of time using his words when he preached, “sometimes preaching in up to five villages a day, often outdoors. In the country, Francis often spoke from a bale of straw or a granary doorway. In town, he would climb on a box or up steps in a public building. He preached to any who gathered to hear the strange but fiery little preacher from Assisi.” He was sometimes so animated and passionate in his delivery that “his feet moved as if he were dancing.”
As for preaching the Gospel...