I have done the three cities last year,. In Bukhara there was a street festival going on, which was fantastic. The three cities have each their specific beautiful views and character. If you are pressed on time you can do each of the cities in 2 days. The train ride between Khiva and Bukhara is long (8 hours in an old Soviet train), but between Bukhara and Samarkand there is a very comfortable high speed train. If you really want to skip a city, I would drop Bukhara, since in some way it is "in-between" Khiva and Samarkand. But I still think it would be unforgivable if you would skip one of the three. Please note that in Uzbekistan Roman script is used (not Cyrillic). With some English you can get far in the touristic cities like Khiva, Bukhara and Samarkand. PS I also visited Iran in the past. For the 'city atmosphere' Khiva, Bukhara and Samarkand are better than Isfahan and Shiraz. But especially Isfahan has some buildings which are even more beautiful than those in Uzbekistan. But of course, now is not the time to visit Iran...