I have white "mold" coming out of concrete walls in the tropics. Is there a product that will clean this off and help to kill it?

Bleach kills mold but u should probably call a professional to deal with the mold problem

The product I use is Polycell MOULD and MILDEW cleaner, it works for me.

This is probably not mold at all, but efflorescence (http://en.wikipedia.org/wiki/Efflorescence). When concrete becomes wet, the moisture dissolves salts in the concrete. When the moisture then dries on the surface of the concrete, it leaves the salt behind as a white powder, often very fine and fuzzy looking. If it scrapes off very easily with a fingernail and water dissolves it, it's not mold.

You can clean if, if you wish, with plain water. It won't cause any harm, though, so if its in an area where appearance isn't important, you can just leave it.

It may be important, however, to try to solve the moisture problem that is causing this in the first place. The wet concrete can, if in contact with other materials, cause *them* mold or rot. The evaporation of water from the concrete is also adding significantly to the humidity level inside the house. Also, the long-term presence of excessive moisture in concrete can weaken it, ultimiately resulting in spalling and other damage. This can range from a nuisance, with concrete dust and flakes constantly falling to the ground or floor, to more serious structural weakening. See http://homebuying.about.com/od/glossarys/g/Spalling.htm.