If you want to experience the real Nairobi, stay at Blue Hut hotel Nairobi Kenya.
They are right in the heart of the downtown area with all the security you want.
The hotel staff couldn't do enough for me when I was there, they were so welcoming and helped us with any request we had.
They got us a very friendly and reliable driver (Erik) who took us all over the unseen parts of Nairobi as well as the more popular places.
There's seating outside the hotel that's just off the street where you get to eat and watch the most amazing activity happening all day everyday.
The hotel is not a 5 star hotel so you don't have many of the luxuries that you would have with a higher rated hotel.
Having said that it is clean, secure, friendly, fresh bottled is left in your room every morning and the it's definitely exciting.
I would strongly recommend this place, I will be going back there again when I can afford it. Mary, Stephen and Eric...thanks for a great stay :)