Actually you're both misinformed. Candida can live in both an acidic and alkaline environment in it's planktonic form but can only exist in it's fungal form if it is no longer inhibited by acid forming (lactic acid) bacteria. These are the types that are commonly found in probiotics. If these bacteria are no longer present the candida creates an alkaline envrironment by producing ammonia which provides the all clear to become fungal. This is most likely when it also forms a biofilm. Ammonia is highly alkaline and is prob resposible for the toxic feeling that many candida sufferers experience.
The small and large intestine are also predominantly acidic, with some areas slightly alkaline. It is the acid forming bacteria that make it this way. This is the same for the skin and other areas of the body such as the nasal cavity and sinuses. The acid prevents pathogenic bacteria and yeasts from becoming a problem, they are part of the innate immune system. This is the same for the bladder. Acidity prevents pathogenic forms of E. coli from proliferating and E. coli is one of the most common pathogens found in the urinary tract.
The sites that propagate the whole notion that alkalinity is the key to health are "sales sites" that are selling Alkaline Water machines or alkaline drops etc. The only thing they would be right about is that the blood stream is supposed to be slightly alkaline.