Actually as a foreigner, you are able to get a better rate.
been here three years, not my experience at all.
yes they'd rather rent to gringos, but they price gouge the hell out of you.
Some years ago, I went to see a flat in San Miguel. The advertised price was 800 soles in ElComercio. My gf went to see the flat in the morning but the owner didn't want to lower the price. A friend of her called the owner as well but the rate was 'no negociable' and he was asking proof of income and references.
I went to see the flat in the afternoon and negotiated it down to 600 soles a month and on top of that free water and electricity. I rented the flat.
I also went to see another flat in Magdalena Del Mar. The price was 650 soles a month. At the time I was there, some other people came to see the flat. But it appeared that the owner prefered to talk to me although I was dressed scruffy as I was helping someone with cleaning and painting her flat that day. And the other viewers were dressed nicely.
Still, I overheard her talking to the other viewers and she didn't want to lower a lot. Only by 20 or 30 soles maximum.
I negotiated to lower the rate to only 450 soles a month.