My landlord's property is being foreclosed. Do we need to file a claim at his bankruptcy hearing to be entitled to our relocation assistance money?

You have same rights with the new bank or lender. US Trustee has to respect it. If you are entitled to relocation assistance money in the current lease, only then you will get it. You won't get any additional or different benefit (than the ones stated in the lease). Again, as Mr. Belli pointed out, all of this is applicable if LL filed BK. If not, the new LL will be the new owner who buys property at foreclosure auction.

First has your LL filed BK? If so that will probably stop the foreclosure until his lender goes to court and gets relief from the automatic bankruptcy stay. It can take them months to do this.

Secondly if the property is foreclosed on you don't have to leave if LA requites "Just Cause" for evictions, you simply have a new LL the bank. In any case you don't have to do anything unless you get a written notice from the new LL which probably will be the bank.