int x, y;
PFont dFont;
void setup()
{
 size(300,300);
 x = width;
 y = 10+(int)random(height-20); // not entire height so the text is allways inside the screen. 
 
 dFont = loadFont("FONTNAME-10.vlw");
 textFont(dFont,10);
 textAlign(LEFT);
}

void draw()
{
 background(255);
 fill(0);
 text("scrolling",x,y);
 x -= speed;
 if(x<-50){ // use x<-textWidth("scrolling") or something here to get the proper clipping of the text
  x = width; 
  y = 10+(int)random(height-20);
 }
}