Using iCloud on Leopard with iPhone 4 I am on Leopard 10.5.8 (my MacBook is too old to upgrade to Snow Leopard) on itunes 10.5, and on iPhone 4 (iOS 5.0). 

I have a MobileMe account.

My iPhone shows iCloud is available in the settings but I don't think I have signed up yet. Should I/can I move my MobileMe to iCloud and still be able to sync my phone to my mac? Or should I wait till I upgrade my mac to a newer version before next June.
If you migrate to iCloud now, you


get all the iCloud benefits on the iPhone
can still access your mail from your Mac (HT4864)
you should still be able to share calendars and contacts (see MacRumors but I haven't had a need to test this yet). This may actually be unsupported by Apple but if everything else fails you could always set up a Google Calendar for this.
will loose all the other MobileMe benefits (like bookmark, pref, keychain syncing, gallery, iDisk etc.)
will still be able to sync the content of your iPhone with your Mac