Last summer I posted an appeal for help with finding a bike to accommodate my unusual rt arm/hand; I can't use a shifter on the right. After reading replies here, I bought a 15 in single speed 29er from Bikes Direct, assembled it in my living room, and the rest is history. It fees great to ride under my own power. 30 miles is no problem on the paved paths around here. Mud, rocks, and tree roots have been a breeze. I am an over 50 mom of 8; if I can, you can.
After spending tme riding the SS bike, I know what I will need if I go to something with gears for longer rides. Also, I know that my muscles will be in such good shape I will leave my friends in the dust!