There are a few deriherus operating here, (search 長野 デリヘル) but they'll accept Japanese customers only. I thought this might have changed with the tightening economic situation, and since there were no gaijin restrictions on a particular site, I gave them a call just the other week. Got as far as time, place, girl, and introductory discount before I was asked my name, and the guy says waaaaaait a minute--not Japanese? No go. He proceeded to get pissy with me and told me that in Nagano Prefecture it's not allowed. (Is he serious? Is this a law? An agreement amongst establishments?)
There is a pink salon a little ways down the alley to the left of Ito Yokado (I forget the name, but you can't miss the tall, garish pink lighting when its open) that will take foreigners if you can speak Japanese. I got the thumbs up, but a buddy visiting from overseas was rejected...and so neither of us ended up trying.
You might also find there are Korean girls that offer full service around the Gondo area. I was introduced to the go-between a year and a bit ago (she was a middle aged Korean woman standing around the streets something like the guys that pull you into the shops around that area) and gave it a try. Not quite the GFE, but what can you do when you're the only white boy in town. After having been shot down by the deriheru, I recently went looking for the lady a couple of times, but haven't been able to find her. I'm thinking I'll either ask the Korean massage ladies if she's still around, or just bite the bullet train down to Tokyo...
Hope that helps!