I don't think there is a way to determine the amount of players, or even an approximate amount that is simple to obtain. Same goes for the amount of total neighborhoods. However, neighborhoods in the Champions League can be determined.
During two 2-week stays in the Champions League for my neighborhood, the rankings after one week were:
- 117,000 during March 22, 2016 to April 3, 2016 (I can't confirm this, as I have other guesses between March and May)
- 123,000 during August 9, 2016 to August 21, 2016
Relatively low amounts of points were posted for the first week of both visits to the Champions League, and staying in the league and also scoring the amount of points above would require a late start - one of my neighborhood's current principles and rules.

