Rather than geting the seeds, just buy the dried flesh. You can get it pretty reasonably off a seller on ebay selling it as "inscence." I don't remember the name, but I have used him before. I think it is peruvian torch rather than san pedro. I have used peyote, san pedro, and peruvian torch, and the latter two are cleaner trips. the peruvian torch also generally has a higher mescaline content than san pedro, but less than peyote of course. Go to erowid and read up on it, there's lots of info about preparation and dosage. You don't want to overshoot the dose too much, unless you like tripping for a long time--18+ hours.

Oh yeah, and mescaline is indeed the shit.