Dumpster Diving in SLO is incredible easy and usually successful!  The Trader Joes dumpster is very hit or miss.  Personally, I have never been successful there, and given what I have heard about people finding food in it, I would rate its' bounty as quite low in comparison to the Sunshine Donuts Dumpster or the House of Bagels Dumpster.  Keep this in mind, because TJ's (Trader Joes') dumpster takes a lot more work to dive than either of the aforementioned two.

Finding the TJ dumpster:

TJ's dumpster is directly behind the TJ's store itself.  Drive or walk around back of TJ and you'll find two dumpsters enclosed by concrete walls butted up against the bushes next to Short St.  Here's a map of the exact location:

Getting into TJ's dumpster:

Since TJ keeps their dumpsters locked, you'll need to bring a pair of pliers to get access to the contents.  In order to gain access, you'll basically be removing hinge pin from the back of the door thus turning the padlock into a hinge to open the dumpster door in reverse.  To remove the pin, identify the small piece of curled wire wrapped around the end of the metal rod at the hinge end of the dumpster door.  Removing this wire with the pliers allows you to then remove (with moderate difficulty) the metal rod from the door.  Once the rod has been removed, open the door (easiest with the help of a friend), and dive away!  

After Diving:

If you use this information to dumpster dive Trader Joe's dumpster, please clean up any mess you make, be quiet and discrete, and be damn sure to return the dumpster to the the original state in which you found it.  Dumpster diving in SLO is easy, and could be made more secure very easily by store owners.  The less that store owners suspect that their dumpsters are being tampered with the better.

Happy diving!