Twenty yards is a very short distance — roughly the length of a large living room or about 60 feet. Walking would take you maybe 10–15 seconds, while driving would involve getting in the car, starting it, and pulling out, which would almost certainly take longer than just walking. Plus, if it's a car wash, driving a freshly-washed car back home through whatever's between your house and the wash kind of defeats the purpose if you're walking the car there... wait, you can't walk a car. 😄
So if the goal is to get your car washed, you'll obviously need to drive — you can't bring the car to the car wash on foot! But if you're just visiting for some other reason, walking makes far more sense at that distance.
As for the Ps in "Strawperry" — there are 2 Ps.