Yes, the majority of hotel reservations are refundable if you cancel prior to the hotel's cancellation deadline, which often is within 24-48 hours of your check-in date. If your reservation is non-refundable, you might be able to still cancel and receive a refund within 24 hours of your booking. Enter dates in and click on "Search", then you can use the "fully refundable" filter to get the best deals near Mount Diablo.