2-3 would be the max if it is a jack o lantern type. Some of the smaller type pumpkin varieties can have 4-5/plant. For me I always start with a small amount of fertilizer. You can always add more, but you can't take any away! Not sure about laundry water...you won't know until you try!

I don't have an answer for your fertilizer question as I'm hoping to get some answers as well. I left SoCal last year and while visiting my sister in LA last week I gathered a few tips for drought gardeners. She keeps 5 gallon buckets in each shower and catches the cold water while waiting for hot water. She also waters her plants using water from boiled or steamed veggies. I thought I'd pass that along.

We are doing the same thing even though we don't need to. With our normal water use, we stay within our allotment. But we still have cut back our water usage in and out of the house. Outside I have cut watering the lawn from 4 times a month to 2 times and still have a somewhat of a green lawn. So we went from 13ccf to 9 ccf.