Aki's, on Meridian Avenue in San Jose, does neat custom decorating work. They did a tin can and rusty nail cake for me one time for a friend who tells his kids that's all he ever got for his birthday when he was growing up. The cake, on the other hand is ordinaire.
Also, no kidding, our local Safeway does good decorating. They actually copied happy birthday in Hebrew onto a cake for me. I'm guessing that depends a lot on local talent, and again, we're talking quarter sheet cake of the most pedestrian sort.
Goldilocks has great birthday cakes. We ordered one and it had 3 different cake flavors built into one cake. The cake was decorated with Winnie the Pooh and looked beautiful. Also, very reasonably priced and delicious. The cake was big, enough for 100 people and only costed around $100.00. It was put inside a big box - very professionally done. It is not overwhelmingly sweet like some of the cheap birthday cakes. But I bet the prices are some of the lowest around. This is one of the exception of the rule where good quality does not mean high prices.
They have many selections to choose from. They even have computerized system to customize your cakes.
I was very impressed. Goldilocks has many branches around bay area. The one I went was in Newark. Just search for Goldilocks or click the link below.