Vice President Joe Biden is in Houston while his son, Delaware Attorney General Beau Biden, underwent medical tests Tuesday.The younger Biden, who is undergoing tests to determine why he experienced weakness and disorientation last week, posted a smiling photo of his wife and himself to his Twitter account Tuesday morning. The tweet said: “Touched by all your well wishes — thank you. Nice evening in Houston w/ Hallie; will share update when we have it.” Beau Biden, who suffered a mild stroke in 2010, began experiencing the new symptoms Aug. 14 after driving to Indiana for a family vacation, said Jason Miller, a spokesman for the Delaware Justice Department. Biden, 44, was admitted to Northwestern Memorial Hospital in Chicago and traveled the next morning to Jefferson University Hospital in Philadelphia to consult with his doctor. He was discharged and spent the weekend at home in Wilmington.Miller said Biden currently is undergoing testing in Houston to determine the cause of his symptoms, but Miller declined Tuesday morning to say exactly where the testing was being done. The White House said the vice president had been home in Delaware for several days and accompanied his son to Houston. It’s not clear how long the vice president will stay, but he’s scheduled to join President Barack Obama in Scranton, Pa., this week during Obama’s two-day bus tour.