This has been explained earlier on the thread. Cleveland will be one of the SAFEST places to have the convention! "Downtown" with the stadiums, convention center, Rock Hall, restaurants, hotels, theater district, casino, can be kept secure for a convention. Larger conventions have gotten rave reviews from participants.
Can it handle crowds? Of course. It isn't uncommon for there to be an Indians game, a concert at the Q and plays at the same time.
We're not perfect, but we're not Detroit or Newark. Have you ever been to Cleveland?
I spent 24 hours in Cleveland in 2005 and found it attractive. I also was able to drive east to Mentor to the Garfield Home. It won’t be a bad location per se; but Republicans will never win much of anything in Cleveland ever again. It was a Republican town before the New Deal.