I am writing this response from Uganda, where I have brought my 24-70 for use on my D700. I have used this lens here for the past two years and in other places such as Sudan, Botswana, etc. I agree with others who say that you should use your best equipment possible, or why have it. Of course it is large and heavy, but the results are worth the effort.
I have never felt threatened in terms of safety and have never found any need to hide or disguise my equipment.