I have gotten or seen this question a few times this cleaning season so I wanted to post for you this information I found.
Dryvit 
is discribed as a textured acrylic finish and as such is a very sensitve product. It is recommended by the manufacture to have periodic cleanings to keep the surface in good shape following these guidelines.
1. Never use an acid or acidic cleaner for general cleaning. Use an alkaline cleaner. They list four products on their website and after checking the MSDS on all of them we can say that our Citrus X-terior will be just as safe and effective as those listed. Our Mighty Max, Mighty Max Plus, Mighty Green and Natures Green could also be used. How to handle efflorescence with an acid is listed later at number 11.
2. Test clean each Dryvit surface with the proposed cleaner in a small and isolated area before commencing to do the larger scope of work for every job. Each type of Dryvit finish is different.
Free Style 
Sand Pebble
3. Do not lean ladders against a Dryvit coated surface as this can cause damage. Think egg shells.
4. Prewet the surface prior to applying cleaner, do not let cleaner dry on surface and rinse thoroughly.
5. Clean from the bottom up so cleaners will not "clean streak" the finish.
6. Use cold water only for cleaning and rinsing, hot water will soften the acrylic finish.
7. Keep pressurized tip angles between 10-45 degrees depending on distance from the Dryvit surface. Ex: 10 degrees when 100 feet above the nozzle to 45 degrees 2-5 feet away. Never use nozzles closer than 24 inches.
8. Use only low pressure, under 600 psi, when using a pressure washer for applying a cleaning solution and rinsing or use a hand pump sprayer for appilcation and a garden hose for rinsing.
9. A soft bristle brush, cloth or mop can be used for agitation to remove contaminants that have been lifted by the chemical cleaning sollution and out of crevices, but not such force that the surface is abraded or removed.
10.If there is evidence of mold and mildew, bleach or similar cleaners should be used so these are killed and removed before any recoating of Dryvit can be applied.
11. If efflorescence has occured due to moisture coming through the dryvit from underlying brick or cement, first determine the sorce of the moisture and stop it, then an atempt at removing the efflorescence can be made. First try a general cleaning with a slightly higher pressure of water to try and remove a light deposit, to using a extremely diluted (1 part to 20) acidic cleaning solution to remove a heavy deposit. As with all cleaning, prewet first, let dwell and a light brushing may be needed prior to rinsing. We would suggest starting with distilled white vinager, or oxalic up to citric acid to be tried.
12. Be sure to thoroghly rinse especially if any acid was used to avoid any adhesion problem for any recoating of dryvit.
13. Surface must be completly dry before refresing the finish or a color change of the Dryvit.
I hope this helps anyone that has a job come up with a Dryvit surface to be cleaned.