The reclaimed water will be just fine. I’m sure they at least screen or filter it. They usually use that same water to resupply those same houses to irrigate again. It’s a separate line from there regular use water. If it wasn’t filtered it would clog up the sprinkler nozzles.
I’d do what was already mentioned and consider talking to people along the route and asking about hooking up to their water. If you use 300’ of hose you’d only need 2-3 homeowner’s to agree to it. Pay them $20 each and a discount on a washing service.
Another option is just staging a few ibc totes the night before. It’s not a whole lot of square footage so might not be worth it though. As long as there’s in street parking you could stage a few along the side and use some parking cones. If you don’t have a couple extra water tanks laying around I wouldn’t buy them just for the job. Although, you’re probably charging a premium for having to haul water so you might want too. Just thought I’d throw a few options out there in case you haven’t thought of them.