The RV parking area for Main Street Station has a laundry facility. Never used it but others have posted they have walked over and did.
If you have a car: There is a laundromat at the SE corner of Tropicana and Eastern. Next door to the laundromat is a Dollar Store. You can buy detergent and/or bleach for $1 and do your laundry. After 2 hours, donate your leftover detergent to a local in the place and leave. I use it every trip I plan that's longer than a week.
If you're staying on the strip you only have to go up tropicana to UNLV and there are a lot of places open 24 hours a day to do laundry Sent from my SM-G900V using Tapatalk
Nearest coin laundry to downtown properties is Busy Bee laundromat on Stewart and Maryland Pkwy. Around a 10-15 min walk. Having said that, I always bus over to either Flamingo and Jones (West Flamingo Fluff and Fold) or Charleston and Decatur (Magic Wash). Both are clean and have wifi.