as most have noted, you shouldn't "power wash" the vinyl.

I use the outdoor bleach and Jomax cleaner mixed together, sold at Lowes/Home Depot. It's an hour job and costs me about $10. But there are several good folks to do it without the "power".

It's mostly to keep algae/mildew down, not so much the dirt.

Not here to push my company so I wont even mention the name...but....dont be fooled into thinking the only way is with citrus or low/no pressure. The only way to get a good rinse and get all the bleach and soap off a house is with a pressure washer with the right nozzle/tip which allows a lot of water but under very low pressure. A power washer with the right nozzles will pump 5 gallons per minute at the same pressure of your garden hose.
Citrus based soaps will not cut thru mold/algae so we ALL use bleach in the solutions. The cheap splash and dash guys use low cost equipment(low pressure electric pumps) to spray watered down bleach on your house and the rinse with your garden hose....noy a very good wash.
A quality company will have proper power equipment, different nozzles for different pressures from high to low, a professional house wash soap mixed with bleach as needed based on the level of mold on the house, and a variety of brushes and equipment. We even go as far as hand washing your windows to insure spotless windows(extra 10 minutes goes a long way).
If you have a stucco house, theres no way you are getting it totally clean without a professional house wash soap of some sort, bleach and PRESSURE. yes PRESSURE. Without the pressure you will never get all the dirt out of all the nooks and crannies of the stucco surface.
Just remember you get what you pay for. The extra $5 or $10 may go a long way with quality soap which has wax in it, and minimal bleach useage and with proper washing techniques.
any questions...feel free to P.M. me or ask here...I will not ever try to solicit a sale....plenty of work out there, just trying to help people out. :)

ALCOA--the vinyl manufacturer, reccomends diluted bleach as part of cleaning solution..so I am sure it is safe and wont harm you siding or void warranty---when mixed properly.

The way these homes are set up, the back of my neighbors house is facing inn my back yard. What is the protocol for pressuring in this instance??

I use Steve's Onsite Services. Excellent service, wonderful couple to work with.

Their # is 352 603 6402.

Eileen