If you want to be considered for the position, you should avoid saying you cannot work weekends when needed to meet a deadline. The interviewer wants a team player who will sacrifice their weekends to help the company succeed. If you have a reason you cannot work weekends, explain your reason and tell the interviewer you can try to make arrangements to make it possible to work weekends, showing your willingness to help.
For example, suppose you have a class every Saturday as you work towards receiving your bachelor's degree. If you explain that to the interviewer and tell them you will see if you can make up the class when you are needed at work, it shows the interviewer you have professional goals and a desire to help the company succeed.
