Since you've basically outlined an area consisting of thousands of square miles, I say

35°25'29.7"N 116°01'58.7"W

I am throwing a goodbye party in mid august and am looking for a place that meets these requirements.

1. Big enough to hold 20-30 people without it being cramped

2. secluded enough so no cops show up ( it might get wild and we dont need johnny law ruining things)

3. if for rent, under 400 bucks