The BBC's The World programme, Tijuana, Mexico An intense debate is under way in the United States over what to do about illegal immigration. The Senate is soon to take up the issue, studying a controversial bill that would see the construction of 1,130km (700 miles) of fencing along parts of the border with Mexico. People along the western edge of the border, south of San Diego, have been living with a barrier for the past 16 years. Franc Contreras travelled there to ask people on both sides what the divide means to them. More barriers like this one could...