Question about bicycles (Mexico City)

Hi!

My husband and I just moved to the D.F. We are thinking about purchasing bicycles. Does anyone know of any good/affordable bike shops to recommend? We are living in Coyoacan. Also, does anyone know of bicycle laws--I have seen many people riding on the sidewalks here so I assume it is ok, and frankly with the traffic I would be a bit terrified to ride in the streets.

Thank you for your help!