RESIDENTS LEAD LIVES OUTSIDE INSTITUTIONS.(Main)

When Mike Pezzula got home Thursday afternoon, he went upstairs to his bedroom to relax and listen to WTRY, a rock 'n' roll oldies station.

Downstairs, Lisa Aerwin was padding around the kitchen in her pink bedroom slippers, washing up and helping get dinner ready. Down the hall, Sara Killen carried some clothes from the laundry.

Dan Heck was probably entitled to just hang around this afternoon. Because Thursday was his 51st birthday and during the four decades he spent in state institutions for the mentally retarded, they never celebrated birthdays. Last year's party at the group home was his first.

"I never got birthdays at Letchworth," said Heck, …