We were at PBH just after the 4th of July. It is supposed to be a much busier time than the week you are going. (In many places, the kids are back in school.) We went to Mama Della's on Saturday around 6:00 pm. We were one of only 4 parties in the place the entire time we ate. (We were there a little over an hour.) Things certainly did not seem to be picking up by 7:30. Now may be it was people are trying to eat more cheaply, but we never had trouble eating anywhere during our week at Universal and PBH. The only reservation we probably needed was for lunch at Mythos. You can make a reservation ahead of time to feel safe, the concierge at RPR should be able to do it the day you check in. By the way, my mother-in-law is Italian and my husband loved the food.
BTW, if the music you are referring to is the Music of the Night in the plaza, the performance takes place around sunset every evening. When we were there in early July, that meant 8:30.
