Why is it the fiesta area and adjoining parking lots (west side of La cholla) are closed and gated most of the time now? Very random days I find one or the other unlocked. It still is part of the park correct?

Security reasons

Those areas are popular with the kids. And there is excessive vandalism. So those areas are closed until further notice.

...It is part of the park, it is closed for security reasons!

Yes there should be in fared cameras inatalled

Call the city

This area is for designated fiestas, foot traffic is clearly visible at times, but vehicles are prohibited.