I was there just a week ago, though not shooting b&w. In general I found it best to steer clear of the National Park areas- the beaches aren't great and the access to them through unattractive wooden walkways. In general I found it easier to find attractive barns and farms etc in the east and south of the Island, but I agree with the poster above that its not systematic- you just have to keep driving till you see what you want. Central Charlottetown is worth a look. There aren't too many towns on PEI - and of these you probably don't want to photograph in Summerside, and Souris is currently messed up by major road reconstruction. I did quite like Kensington and Victoria but they are little more than villages really.
If you're going soon you must expect much of the accommodation and restaurants etc to be closed for the season.