Yes, here's a place I've been. I passed through there very briefly two years ago, while on the way to a week-long jungle retreat. The jungle retreat was nice, but there weren't any girls. I visited a few extremely tiny villages along a tributary river, and the young women there were very shy.
Iquitos seemed to be a different story. I was travelling with a tour group of Americans, so we arrived into the airport at night (the airport is on the very edge of the city). Then we took a motorcycle taxi (these taxis make the city seem like Thailand) to our hotel along the river. A very beautiful Peruvian girl was working at the hotel restaurant, but that's to be expected at a nice hotel. In general, most of the women weren't the best-looking (face-wise), but I did get a chance to talk to a few of them the next morning, and they were extremely easy to talk to.
A bit about me: White, brown hair, bluish-green eyes. I get complimented by women on my eyes EVERYtime I visit Latin America. So, I do get a lot of mileage in Latin America because of my physical features.
Our group had a couple hours to kill before getting on the boat for our jungle retreat, so we went to the nearby open-air market with armadillo butts covered in flies and that sort of thing. The whole time walking through the market the Peruvian female guide I was with kept pointing out the fact that ALL the local women were looking at me. It was actually quite unnerving, because I had never experienced anything like that before, and the guides also kept saying how seedy Iquitos is. My female guide kept telling me to keep my hands in my pockets so no one would rob me.
Despite the seediness, I would have liked to go out solo to some club. Based on the eye contact from the women during the day, I'm sure it would have been one of the easiest places in the world for me to get laid. Sexy women were pretty consistent. If you don't get hung up on the faces, many women there have great bodies. I can't say anything regarding names of places, and I was only awake there for a few hours total, but I got the sense that a guy who looks like me could have a blast.
After reading through the forums, I would say Iquitos is probably the Spanish-language equivalent of
Manaus, Brazil.