What would the rough hash rate for an ec2 instance be - litecoin
It may not be as high as you expect with out compiling CPUMINER for multi core.
I can not tell if the last on the list is the same or a slower version of what you are referring to from this list online.

http://litecoin.info/Mining_Hardware_Comparison#Other
based on that page, each Amazon High-CPU Extra Large Instance, running Ubuntu 12.04.1 and using pooler's cpuminer 2.2.3, has a script hash rate of 38 Khash/second. Rounding down ( habbit, no real math reason other than the real world is usually slower ) to 19 times that makes it an estimated 722  Khash/second and possibly faster.