Baked in the Sun at the Marketplace has great birthday cakes. Just stop by and pick out what you want when you get there, as long as you give them 24 hour notice.
You've already gotten some great advice, so I'll just second the recommendation: Baked in the Sun! They have delicious made to order cakes. They're on the third floor of The Marketplace, and their number is 693-8786 (just don't call during lunch hour as they get quite busy!)
I had a cake made from Baked in the Sun last April ad it was incredible. My husband wanted a very specific cake. Chocolate cake with strawberries and bananas and whipped cream in between the layers.
The were worried about getting fresh strawberries, but they did and the cake was incredible!