Me, a shotgun, and two shells vs. an ass load of zombies. Aye, sounds like an even fight it does.
I'd empty the shotgun, flip it around and go Lycan. Seriously, there is no stopping me when I hit beserker mode. Every zombie would be dead. I might escape with a few scratches, maybe some serious wounds, or I might die. But dammit I'd rather go out bat-shit insane than cowering in a corner praying for help.
EDIT: Smart and not so badass way: Jump in the dumpster, fire a round near the bottom stick the barrel of the shotgun out and push. I might not go very far very fast but as long as the zombies dont find me I should have enough time to make my way down an ally.