Upload & Sell: Off
The guys at the market are mainly Pakistani, Indian and Bangladeshi. They generally understand only very basic English. As there is a Cricket 20-20 World Cup currently being played, mentioning cricket is a bit of an ice breaker.
So I'm literally just asking with a waggle of the camera and thumbs up or thumbs down to see if they would mind having their photograph taken. If no, it's just a case of smiling, saying 'thank you' and moving on. Probably around 80% are more than happy.
These guys don't have internet or know how to use it, so getting to their pictures is not an option online. However I go back from time to time to take prints to distribute. I haven't done this yet at the Fruit and Vegetable market, but I'll be doing that next week.
So all in all, from getting the thumbs up, it's generally a 30 second exercise from taking the picture and showing the results on the LCD to moving on. With the candids and more 'street' shots, I don't ask for permission and just observe and wait for the moment.