Just try all the unis and private schools the first few weeks of term (register but say you have problems with your credit card or something) without paying and then see which one at your level has the best teacher and the least people in the class. If you pay upfront first and then you don't like it, you probably won't get your money back.
Yunnan Uni at lower levels has huge class sizes. Yunnan Normal Uni seems to have a much better infrastructure and smaller class sizes. Both have large nos of eastern students so you get to practise your Chinese more. Kunming School of eastern languages on wen lin jie has mostly western students, less people and is cheaper, but you miss out on the whole uni thing.
Like I said, just try them all and pick the best.