We 've spent two nights in Guesthouse Raha Leo, the night before and after our safari. We were pleasantly surprised by the peace and cleanliness when we entered the guesthouse from the crowded, noisy and polluted streets of the Arusha city centre.
Two brothers are managing this place and they are very friendly and make you feel at home.
The room was basic but was clean and looked like a proper hotel room, and considering we payed only 30.000 Tsh (app. 15 euro) for it, this was great value for money. Also breakfast was included, incl. fruits and eggs.
Don't expect the most splendid or nicest hotel that you will find in Tanzania, but for a budget, clean accommodation in the center of Arusha we would definitely recommend this place!