The hotel costs are part of your claim.
The HOA will be liable if the evidence shows that the cause of the water damage was due to common area pipes.
The upstairs owner will be liable if the evidence shows that the water damage was due to plumbing within the upstairs unit.
If the insurance carrier for the upstairs unit does not pay you, then you will have to sue the owner of the upstairs unit and/or the HOA for your damages (property damage plus hotel costs). You don't sue the insurance carrier. It will be your burden to prove which party is liable.
The information presented here is general in nature and is not intended, nor should be construed, as legal advice. This posting does not create any attorney-client relationship with the author (who is only admitted to practice law in the State of California). For specific advice about your particular situation, consult your own attorney.
you need to make claims with the upstairs owners insurance company and the HOA's insurance company as well and let them fight out the cause. I have handled cases such as this before. Please give me a call for a free consultation at 415-441-1052.