Perhaps it’s just wishful thinking, but talk is circulating that heart-bypass patient David Letterman will return to his “Late Show” desk much earlier than expected. How early? How about Valentine’s Day. (Valentines, heart . . . get it?) It also helps that Feb. 14 is part of this month’s ratings sweeps period. Not even three weeks after his quintuple bypass, a rapidly recovering Dave stopped by his New York office for a two-hour visit on Monday. Dave reportedly drove himself to the headquarters of his Worldwide Pants production company, and he looked just fine — if you like him in a beard. Whether or not Letterman, 52, will be up to the chore of hosting a show is up to his doctors, who originally said Dave would require six to eight weeks of convalescence before returning to his job of delivering monologues, spouting Top 10 lists and goading celebrity guests.