Orange County Fair Grounds?

I am so bummed. My granddaughters are visiting from Germany and will be leaving August 4th. I have told them about the Orange County Marketplace. They are so looking forward to going. BUT I just found out that the Orange County Fair is there and the Marketplace will not return until August 11th. Does anyone know where all the vendors go when they are not in the Marketplace? Or is there another place between San Diego and Los Angeles that has just as many vendors as the Marketplace? We are not interested in going to the fair.