Registering for Meldebestätigung (Berlin)

Hello,
I am a US citizen married to a UK citizen. We are moving to Berlin in July, and have arranged for a 2-month sublet when we first arrive.

My husband will be working, and I plan to look for a job once we've settled in. I can stay for 90-days without a residence permit.

My question is: Do we need to register for a Meldebestätigung within the first week at the district office near our sublet?

Or, should we wait until we have found our long-term rental?

Thanks!
Michelle