I really think it depends on the dealership, I know Hoehn isn't open on Saturday's but I've definitely been to Escondido on Saturdays so I know they are.
Mike is right it would definitely be worth calling Penske to see if they are open since I'm sure they're closer. I also know the dealership is brand new and very nice!
02 C32 AMG
84 190E 2.3 5 Spd