Should be a walk in the park.
Pretty much a park and grab at Los Paseos Park off of Santa Teresa Blvd. Container is a magnetic key hider. Be careful, lots of activity in this area. Please follow park rules, closed 1 hour after sunset.
Updated the hint to make it a little easier. 1/10/15 Upped the difficulty on this one. Not intended to be a challenge, but it can be tough to spot. 10/15/15 Don't need to go in between the large objects.... it's not in there! 10/26/15 Checked and it was missing. A replacement is now in place. 1/20/19 Checked after some DNF's and it was missing. A new one is now in place.