Water content of the vegetables has little or nothing to do with Teflon deterioration. The reason you add wet vegetables after "dry" ones is that the water content of the wet vegatables will prevent the dry ones from searing and carmelizing.
However, more to the point of the question, the way you should fry or saute vegetables in a non-stick pan is:
- Pour oil into the pan
- Heat the pan and oil to between 300F and 350F
- Drop in vegetables
That being said, I personally use stainless or cast iron if I'm just frying vegetables.
EDIT: I previously posted some incorrect information about acidity and Teflon. I have removed this information based on research. As it turns out, Teflon is highly resistant to acids and would not be damaged by acidic foods in any way -- it can resist hydrochloric acid. Reference: http://www.calpaclab.com/pages/chart.html