OK, I really want to visit Morelia but am a bit concerned about spending the night there due to recent State Department warnings. So I am considering the possibility of making a day-trip there from Queretaro. Is that doable (and safe) by public bus? And if I am able to get to Morelia by around 10:30 AM and leave around 5:30 PM, will that be enough time to see a fair amount of sights around the UNESCO-listed historic center? Any advice in this regard wil be highly appreciated!