This cache is placed in the Barry Goldwater Range, and a range pass is required. It can be obtained at the Marine Base or through the mail. You can use this link for the pass, but do allow about 10 days to receive it.
http://www.yumaevent.com/RangePermit_byMail.pdf
Remember this is desert...carry plenty of water...emergency supplies...protection from the sun...and let someone know, where you will be going.