Looking for reference for Apples A5 cache size
Detailed specs on Apple's processors for iOS devices are usually not mentioned. Mosty likely as Apple's focus is on a product's performance as a whole. Mere numbers for memory, cache and clocks don't reflect that.
Therefore, even a professional blog such as AnandTech draws such information from running a GeekBench test:
L2 Cache is 1MB and shared among both cores.
But note that these are not official numbers confirmed by Apple.

[picture from AnandTech]