We parked on the gravel closest to the casino and was too far away from the wi-fi, so you must have to park closer to the RV park. I would still continue using this lot despite the $15 fee. No broken down 'living there' RVs anymore. Very Large Level gravel lot.
(Editor's comment: Well that's a shame, $15 isn't bad for non-gamblers, but I expect a lot of people leave more than that behind in the casino. Thanks for the report!)