As I have shared my grocery bill each week on this blog, I have become aware that having two kids in paper diapers is MUCH more expensive than having 1 kid in paper diapers.
When my oldest daughter was born 21 months ago, we briefly tried to cloth diaper her. (We already had all the supplies because we cloth diapered my son from 6 weeks until he was potty trained one month before he turned 3).
However, some variables made it difficult to cloth diaper her—we live in a 3 flat apartment, and all floors share the same one washing machine. Our new neighbor had an elderly dog that was prone to accidents, several a day, so it was not uncommon for her to monopolize the washing machine for a few days at a time. That does not work so well when cloth diapers need washing. Also, we figured the laundry cost we had to pay ($1.75) per load, was not that much cheaper than buying paper diapers on sale.
Now that we have two little ones in diapers, I am feeling the pinch as much grocery budget routinely is $90 to $100 a week. Also, my neighbors dog has passed away, so she hardly ever uses the machine now.
So, I have decided to experiment in the month of August. I will cloth diaper my girls the entire month with the exception of the five days we will be visiting my mom. I will also use paper diapers for night time. (That will only be two a night as both girls sleep through the night.) At the end of the month, I will add up the cost and time difference.
I should state that my husband is generally not on board with this. He is finishing up his Ph.D. and thinks we are already too busy to mess with cloth diapers. We will see what he thinks at the end of the month. I will report back in early September.

Good luck on your cloth diaper experiment. I too am going back to cloth not to save money as I only have one in diapers but when I cloth diapered my last one she it helped me speed up the process of potty training. I am slacking in that department this time around plus I have tons of cloth diapers just sitting there that I made not being used.
I might suggest getting a diaper sprayer. AKA multi-use sprayer. I have two kids in diapers, too, and have found it to be really useful with the cloth diapers. I have a picture at the below blog.
http://recessobsession.blogspot.com/
Good luck! I find the cloth has worked really well once I got the husband on board!
I also live in a three story condo. I have a very similar situation (Husband just finishing up law school…) Our laundry is about $2 a load (I wash the dipes twice, once in cold and once in hot since I can't do an extra rinse cycle, bla bla…) I would second getting a diaper sprayer, it will allow you to decrease the freq. of washing and keep the smell down. I would also encourage you to use diaper liners. (this is my wednesday blog post, check it out on Wednesday) Sometimes DD will just stool and not pee and I can just pull out the liner and put the same dipe back on. (hard stools) she is two and nearly potty trained…the saving on the latter end is significant. Also I have two in cloth and it is very easy to just wash their dipes together. Long comment short…get a sprayer and or use liners. (check out my post on frugal liners on wednesday.)
Kristina
http://thecrunchysoup.wordpress.com