You might be able to ask the hotel to accommadate a later check-out, so you can come back after your interview and get your stuff.
If not, most places will let you store your luggage at the hotel front desk for the day, so you can pick it up on your way out. This is what I did, which was pretty convenient since I had to come back to the hotel to catch my shuttle to the airport.
Also, some admissions people will let you leave your luggage in their offices, but it seems like it would be a hassle to take everything with you the morning of your interview.
Good luck!