S100 is great for the really grimy parts, but it's expensive also. Just spray it on, let it sit for a minute, then hose it off. Crud just melts away.
There is no problem using alcohol on Lexan (polycarbonate). That's what we used to clean the Lexan when making F-16 canopies (used 99% isopropyl). Just follow the alcohol wash with distilled water and give it a good dry with a microfiber cloth or a cotton baby diaper.