Hi @cappled1989,
I definitely understand your desire to kill two birds with one stone. However, I agree with Jon here. CS courses are rigorous in their own right, but not necessarily in the way adcoms want. Let me give you a little context. An MBA curriculum is designed to be fast paced (they don't want you to waste your ~$5,000 a class) and building on knowledge you should, theoretically, already have. If you don't have the foundation, you're going to struggle. For example, if you don't have a solid grasp of statistics, you're not only going to have to take the basic stats course which may not be why you went to bschool, but you're going to struggle in other courses as well. Everything from finance to marketing uses advanced stats and, potentially, regressions. Taking courses that align well with the bschool foundation are what they're looking for. A CS course, no matter how difficult or applicable, won't necessarily enable you for success IN the program. Does that make sense?
@becs5213,
Go the extension route. Coursera, at the moment (they may evolve and this may not be true in a couple of years), is not a substitute in the eyes of most adcoms for alternative coursework. Also, UCLA's and Berkeley's courses are well known and convey not only an alternative transcript, but dedication.
If either of you have questions, let me know!
Bhavik