Question: Can we have breakfast early if we must leave before breakfast is scheduled?
Answer: This varies from inn to inn. Remember that bed and breakfast innkeepers are professionals who have their own schedules they need to tend to, and that they often do not have any staff to help out.
However, most innkeepers will try to meet your needs. If a full breakfast is not possible at the time you need to eat, perhaps a continental breakfast would be an option. It certainly does not hurt to ask.

