YES! In fact, a lot of US citizens already live in Tijuana. But here's the catch: they work in the US (i.e. San Diego). Many Americans found out it is possible to live in Tijuana (or Rosarito) and still work in the US and get US dollars income. You will see many expats in Tijuana crossing the border daily. They chose to cross the border daily because with the USD salary, you can really live well in TJ.