Hey there,
Tamale is a wonderful place to live. I was there for four months a couple of years ago, and just went to visit again this past week. There are lots of volunteers and ex-pat NGO workers in town, so you'll have no problem meeting people even just by wandering the street or heading to the Vodaphone internet cafe (it must be the best in town). If you're looking for a place to stay temporarily, I recommend TICCS guesthouse. Also definitely buy/rent a bike. Nearly everyone has a bike or motorbike in Tamale and they make getting around a lot more fun.
In terms of weekend trips, I recommend heading to Mole (elephants), Larabanga, Wa (hippos), and Bolga....
Really, Tamale isn't too big. Just wander around and you'll find lots of great nooks on your own.
Have fun!