Walk the Line (20th Century Fox, 11.18), the Johnny Cash biopic with Joaquin Pheonix and Reese Witherspoon, may do better this weekend than tracking figures are projecting, which is somewhere around $15 million. Surveys of moviegoers tends to focus on the big cities and miss out on the views of folks from the boonies…red-state pickup-truck country…which is where a lot of Cash’s fans live. Figure something closer to $20 million, give or take. The big champ, of course, will be the Harry Potter film, but nobody cares about that..ignore it.