David,
I'm going to Las Ventas on August 8th and I'm also arriving that day in Madrid. I looked at
www.las-ventas.com and it looks like for both August 1st and the 8th, they are have Novillada con Picadores... meaning that these are unseasoned rookie matadors. I'm expecting that it won't be too difficult to get tickets at the box office the day of. If I miss it though, I'll try a corrida at another city.