tourist to Z visa

Hi I am a US citizen who is waiting on my new job to complete the application and documents for Work Z. Since I am leaving NYC and going to Seattle (before going to Shanghai) where there is no Chinese consulate, I have a couple questions -- is it possible to mail in my documents to NYC or SF consulate/embassy to get my Z? If not, can I enter Shanghai a week earlier with a tourist type and then leave the country for a couple of days (like go to HK) and then come back with my Z?