You can eat the orange fruit from one of them but to be honest its pretty tasteless and full of seeds.

If P. caerulea does set fruit in this country, they are often devoid of any seeds and pulp also and the orange skin is almost inedible anyway. If you are (relatively lucky) and there is the pulp surrounding seeds inside, they are edible but not a sharp and tangy as P. edulis which is one of the types you buy in the shops.