New Yorkers may be able to surf and ride at the same time if a plan to put iPads, or a similar device, in the back of taxis takes off. A San Francisco company, Square, is proposing a pilot program to install tablet computers in the back of 50 taxis, replacing the little-loved miniature television screens used in all cabs since 2007, showing commercials and some news and entertainment clips. Riders would be able to make Internet searches, play games or shop on the tablets. Square is due to present its plan to city authorities next month.