Our flight arrives at 11:00pm at LA. We then have a transfer from the airport to the hotel. Is there a late check in policy as we probably will not arrive at the hotel until 12:30am.

Not that I am aware of but you should check with the hotel directly to be sure.

We checkedin kind of late too when we were there. The safest for you is to call them to be sure. Because I don't know for sure.

you can leave your bags without problems

Yes. U can go anytime if u already have reservation.

If you are a Bonvoy Member, you should use the App to check-in. The app lets you indicate the time of your arrival. Otherwise I would notify the hotel that you will be arriving early morning hours.