Up Downtown! kicks off the first weekend of summer with a party to celebrate the boys of summer, Buffalo's baseball Bisons. The festivities, which run from 5:30 to 10:30 this evening in the main exhibition hall of the Buffalo Convention Center, will feature giveaways of free tickets to upcoming Bisons games and door prizes donated by the Bisons. Also on hand will be a petition for a major league franchise for Buffalo, which will be presented to Baseball Commissioner A. Bartlett Giamatti at the Old Timers Game June 19 at Pilot Field. Musical entertainment includes the Top 40 group Niagara and deejays from WGR-AM and FM.