Well, if you are staying in Tempe, you should be able to cache to your hearts content no more than a few miles around you!
Weather depending, there are a few good ones that can be had.
There is Papago Park, and South Mountain Park, and a plethora of urban hides just about everywhere (this is my local stomping ground)
If you go east a bit, you can make a find for GC57 (a little tricker this time of year - it is open desert, and you need to be prepared for that type of hike - about 5 miles round trip)