The location of LaBocca has been offered fairly sincincly in this thread.
Try again: if you stick your head out of the main Complex entrance (the entrance in which resides Poseidon) you simply look across Thappraya Rd and then look a bit to your right and you'll see LaBocca.
You can't possibly miss it.
LaBocca also has a website which gives you the address. Also Googling -- AKA 'Paborn's Frightful Nightmare' -- will get you many references.