If you are meeting up with people in the middle of Chengdu, meeting at the statue of Mao on TianFu GuangChang (TianFu Square) is OK. You can sit on the steps and watch the thousands of cyclists and pedestrians, and, less attractively, watch the building work on the underground system.
TianFu Square, north side - can't really miss the statue - very large. Be careful about the China Mobile clock to your left - it's often wrong.