Subway and Taxi transportation in Shanghai

Deaar Emma: My sincere thanks for your prompt reply to my questions. You are so kind and wonderful person. Some people said that it is difficult to find a taxi in Shanghai. Do you always have to ask the hotel to call a taxi for you? Or can you just find them on the road when you need one? Also is the subway easy to use and cheap in Shanghai? How do we take subway from Yu Yuan Garden to People square? Approx how much will it cost? Is the cost of the subway depends on how many stops you travel? Your time and assistance are much appreciated! Diane