I am trying to urlencode this string before I submit.
queryString = \'eventName=\' + evt.fields[\"eventName\"] + \'&\' + \'eventDescription=\' + evt.fie
Try requests instead of urllib and you don't need to bother with urlencode!
import requests
requests.get('http://youraddress.com', params=evt.fields)
EDIT:
If you need ordered name-value pairs or multiple values for a name then set params like so:
params=[('name1','value11'), ('name1','value12'), ('name2','value21'), ...]
instead of using a dictionary.