Being flexible with the schedule you are willing to work is always a plus. However, many people work more than one job or have a one parent home which requires them to have a flexible schedule. Others simply prefer to work one shift rather than another. Being upfront with the interviewer about what schedule suits your preference could help prevent conflict later on. It is easier to plan a schedule you can agree on than it is to fix problems that arise due to fear of being rejected. Be honest and direct.