That's cool if you are lucky enough to find them and identify them correctly. P. cubensis does OK on poo, but it does great with just some coco coir instead. It's a mushroom that loves to be cultivated. The Pacific North West is really the ideal location for finding wild mushrooms. (You can find them all over the place, but there is a ton of luck involved.)

Honestly, I would rather forage for p. semilanceata, aka, Liberty Cap. It grows in regular grass next to streams or ponds and not necessarily in poo. They are generally a bit stronger but also a bit smaller. With the exception of one look-alike that I know about, they are easier to identify.