I have to wait 90 days on the iTunes music until I can download my music onto my ipad 2 what should I do?

What is the error you received

I assume that you have two iTunes accounts and that you've logged in with one of them and re-downloaded past purchases ? Downloading past purchases links that device to that account, and you will need to wait 90 days before you can log in with a different account and download past purchases from that as well - the 90 day timer can't be overridden : http://support.apple.com/kb/HT4627

I think that it's designed to stop other people logging into somebody else's device and downloading all their past purchases i.e. sharing music etc.

If you have content from both accounts on your computer's iTunes then you could try syncing it from there (but note that re-downloading past purchases from an account on your computer's iTunes will also start a 90 day timer on it).

Wait 90 days. Nothing else you can do short of selling your device and buying a new one. I did that with my Mac last December when I got the message. Sort of drastic but I did it.