Last November, Boynton Beach city officials held a watch party to demolish its city hall building to call attention to their ambitious $250 million Town Square project, which includes a new City Hall, along with a library, hotel, cultural center, amphitheater, apartments, parking garages and a fire station. The big project is proof of a changing Boynton Beach, a city of 77,000 residents that is slowly shedding its sleepy retirement past and reinventing itself as a modern-day municipality. The March 12 elections represent a chance for voters to give a thumbs up or thumbs down to the direction of their city under its current mayor and commissioners, who serve three-year terms. They have a choice of five candidates in the race for mayor, including an incumbent, and a host of candidates competing in three of four commission seats, including two incumbents.