Can I return to 3.1.4 version of WP if site fails?

Hi:

All but one of my WP sites are hosted by Bluehost and the upgrade to 3.2 etal was no problem. But one site is hosted with an outfit that has not previously hosted wp sites. They assured me that they would update their PHP etc. to support 3.2 but they haven’t been entirely reliable to date and we’ve encountered problems. If I do the upgrade for my client and things don’t work, is there a way to go back to 3.1.4? If I copy the entire current wp installation, would I just replace with that? Or is there a particular folder(s) to copy?

What’s the best way to proceed?

Thanks!