The 37-year-old will leave the American club after the MLS Cup final next month and has already been linked with a host of clubs around the world.
The name of West Ham too has been mentioned, but Allardyce says that at the moment it is "speculation".
"David has always said to me when he has been available that he only wanted to play for Manchester United in this country, and I haven't heard him say he wants to come back to England," he said.
"It is speculation until David decides where he wants to go. I am not so sure about the situation at all.
"If David said he wants to come back to London in the Premier League, we would talk about it. I don't want to say we will or we are. It is speculation."