Metro line 2? As I know, the Line 2 doesn't have a stop at Xujiahui. If you are in Xujiahui currently, you could take the subway Line 1 to Shanghai South Railway Station firstly. Here, you could take the shuttle bus Line 7 to Pudong Airport with a fare of CNY20.

Although the shuttle bus Line 3 passes by Xujiahui, I'm afraid that there is no seat left for you.

No free shuttle bus and Subway Line 2 did not pass Xujiahui, it is Line 1. If you mean airport shuttle BUs Line 2, I think it did not get to Xujiahui also. It should be bus line3. It stops at Zhaojiabang Road, in front of Xujiahui Park. You can take it to the airport and it takes 1.5 hours. To be faster, you can take subway from Xujiahui to People's Square by Line 1 and change to Line 2 there to Longyang Road. THen take Maglev train to Pudong airport. If you can find the bus stop, it seem easier for you to take bus.