When should vendors plan to arrive?

Does your venue have a kitchen area or is everything outside? If you have a kitchen area and it is away from the ceremony site then you shouldn't notice them. BUT if like my venue where everything is outside in one location then they should be set up before your ceremony starts. They can cook or prep the main meal during cocktail hour but they need to be ready for cocktail hour before your ceremony starts

My caterer is coming at 3:30 pm and my ceremony starts at 5pm. All in all you are paying for a service and you should voice your concerns if you want them there earlier.

Our venue was a full service hotel, so we had no issue. I wouldn't know why you'd want it set-up food hours before it's served, giving it a chance to dry-out or go bad?

I attended a wedding where someone thought it was a bright idea to set-up the cocktail hour food before the ceremony, on a porch, in hot weather. Result - sweaty cheese, squishy fruit, dry raw vegetables, and stale crackers.