Sofar the plan is to have 4 dives in Menjang, 4 in Tulamben and the rest is still open .
I can recommend Biaha and Mimpang, although they're a bit more challenging than Menjangen and Tulamben.
My wife and I were in Bali early to mid October last year, and visibility ranged between 50 and 80 feet (15-24 meters).
Menjangen Island is a wonderful dive site ... make sure you've got the buoyancy skills for wall diving, however as portions of the wall descend a very looooooong way to the bottom.
Tulamben is, so far, my all-time favorite dive site. I especially enjoyed diving the USS Liberty, although it bears little resemblance to a ship anymore. But the structures are massive, and so full of life. It's a photographer's dream. The Coral Gardens (sloping just off the beach from the Paradise Hotel) are a wonderful night dive. At 40 fsw (12 meters depth) we were able to turn off our dive lights and still navigate using the lights from the hotel.
Biaha and Mimpang are both boat dives ... we left from Padangbai, situated between Tulamben and Kuta.
Biaha is a very beautiful dive, although we encountered a great deal of surge. It's more of a steep slope than a wall, totally covered with corals and sponges. There's also in interesting cave nearby where you can see white-tip reef sharks.
Mimpang had the most life of any site we visited ... but a lot of current. Thermoclines at this site were dramatic, ranging from 84 degrees F to 73 degrees F (29-23 degrees C). Make sure to carry a safety sausage, as currents here can carry you far from your boat ... even between the rocks that pass for islands in the vicinity. Even with a sausage, we were on the surface for nearly 1/2 hour before our boat found us.
I love Bali ... I hope to "retire" there someday ...
... Bob (Grateful Diver)