If the soccer field pre-dates about 1960, you should be able to find silver & wheaties (assuming it hasn't been pounded to death by past md'rs in your area). I know some parks and schools in my area, that date to the '40s and '50s, that we used to hunt for silver at, back in the late '70s and early '80s. But you'd be hard-pressed to find ANY silver at them now, since they were just picked so hard back then, when the pickens were easy (assuming we were at schools and parks where depth and junk wasn't the issue). So it's not a "given" that any school or park or soccer field that dates back to the silver days, will *necessarily* produce for an md'r, today, in 2012.
"Old farms" are not necessarily good places to coin hunt either. Not a "given" anyhow, even if they are super old. Because of several reason: back in the old days, before curb-side trash pickup, people on farms just put their trash out in the yards in burn pits/bins. Or scattered the kitchen scraps out in the yard for the chickens to pick at (read "trash"). And the yard was nothing more than a parking lot for tractors, was a work-zone, etc.... Farms were (and still often are) industrial/commerical areas of usage. So unlike city municipal yards, where people tend to keep a neat tidy front yard (and don't use their front yard to store piles of supplies, tin, tractors parking, welding, etc...).
So if it were me, I'd prefer an inner city yard, all things being equal.
