Ask at least 2 or 3 times and reconfirm at every opportunity. In the mountain areas, geared mountain bikes are available and seem, on visual inspection, to be quite good. Puncture and bike repair wallahs are everywhere. Cheap and they do good puncture repairs. They can be innovative with other mechanical problems.
Local bikes are OK for some touring.
They can be rented in the 2 main tourist areas Katmandu and Polkara. It is possible to carry bikes on most buses. Personally supervise their loading and securing to the roof. The bike is definite asset as many of these places are more accessible by bike than otherwise. The people are more 'friendly' and less likely to try and rip you off than in the more touristy areas.