I recently spent several days here when I visited Culiacan from the states on business. My room was booked through a Mexican colleague that was also staying in the hotel. The room was 430 pesos a night which translates to (as of OCT 08) to $32.42.
My room was on the SW corner and overlooked one of the main intersections in Culiacan. It was quite noisy until about 10pm or so then calmed down until about 5am when the traffic started up again. The room was very clean, the maid changed the bedding every day and the bed was surprisingly very comfortable. The shower had excellent water pressure with plenty of hot water available.
The hotel also has laundry service, which I used. It cost about $12 to get 2 days worth of dirty clothes cleaned - very good price compared to about the $30 I pay on average in the states for the same volume of clothes.
There is a restaurant in the hotel - I ate there several times with my colleague. The food was pretty good and dirt cheap. Average dinner ticket for both of us was less than $10.
The hotel has wireless internet but it cut out frequently while I was there - but it was available long enough for me to do my work.
There is a pharmacy across the street and gas station around the corner where I got snacks, bottled water & sodas. I would not advise Americans to stray very far from the hotel without a Mexican friend or two. The immediate vicinity is fine but a few blocks in any direction and things change quickly. Also, stay in after dark for your own safety.
The staff at the hotel and restaurant were very nice. Most spoke a little English and between my poor Spanish and their English, I had no trouble communicating.
The Hotel El Mayo seems to have mostly Mexican business people staying there - I was the only American there to my knowledge.
I highly recommend the El Mayo to anyone wanting a good, clean hotel at a good price while staying in Culiacan.