I think they should always be in fun cities. There is a day off between games after all. I was being lazy with the South and went with markets. I have heard good things about Charlotte, Memphis, Austin so maybe those should be the venues. LA sucks but it is a major market so TV will likely want regionals there.
I have been to New Orleans, Houston, Atlanta and the experiences were night and day. Houston and Atlanta suck and should never hold a Final Four again. Neither should Minnesota, Detroit, or Phoenix.