Even after living in Nevada County for more than two decades, Sally Martinez was shocked when she saw her first bear hanging out in her neighbor’s tree. “I didn’t believe her when she told me,” Martinez said. “But I went over there to look at it. It was very big. It had a big old head.” What appears to have been a black bear was spotted Friday afternoon about halfway up an estimated 60-foot tree off John Born Road near Penn Valley. “He stayed up there for about three to four hours,” Martinez said. “It was up there for the …