What time does the Procrastination Station open on Saturday?

They open at 10am on Saturday. The best place to find the hours for the coffee shop is on the hours sheet located on the desk in one of those plastic sleeves.

Anywhere in the Library where a person can break a $50 bill? Any place on campus?

There is no place in the Library to get change. The Procrastination Station does not break bills, but might have the cash available if you were to actually purchase something. Have the Patron ask before they do it though.
As for on campus most places will need you to buy something in order for them to break a bill. You can also try the UMass/5-College Federal Credit Union in the Campus Center but you need to be a member for them to give you change.

What happens when the Cafe is closed?

This past Saturday no one showed up to open Procrastination Station. Many questions were asked of the student working at the Information Desk and people were upset about it being closed. Any time the cafe has not opened it is usually because the person scheduled called in sick or there was some sort of emergency or oversight. The cafe is separate from the Library and it may be hard to find out what is going on but that is not the job of the Information Desk staff member to find out. The job of the staff at the Information Desk is to try and be sympathetic (don't take abuse though) to the patron who is upset about it not being open. Try to convey that they are separate from the Library and if they are not here it is probably because someone is out etc...
If you have any other questions about this please let me know!