I have a screened in porch; well actually a glassed in porch. It is on the original plans for the house. It has exterior siding on the inside walls and the floor is decking. I don't know why they just didn't put in a sunroom, but they didn't.
Anyhow, the outlets are exterior with waterproof caps. Is that necessary? There is no more chance of them getting wet than any interior outlets; but I know code can be funny.