Hide 'On my iPhone' calendar when syncing with MobileMe
Yes, I think you can change this settings in iCal, as your mobile me settings are in there.  I did this, and my iPhone only shows my Mobile me calendars.  

If you use gmail, I would also reccomend BusySync. It syncs anything you add to you iCal, and then iCal and mobile me syncs.  Its pure awesomeness in my opinion.  

Also, if you have devleoper tools enabled, you can edit the plist mobileme sync-time interval to 1 min, instead of 15.  You can access the mobile me plist file in home/library/preferences/byhost/ - the specific file name is like: com.apple.mobilemesync.. or something like that.  Im at work, and use a linux system, so if someone else knows, please confirm, otherwise i will update this when i get home.