FUBPAXMMD
The cache is hidden somewhere in the city of SF. Some will find the puzzle hard, some will find the hide difficult, others will think both are tough. Bring sturdy shoes and a bottle of water for the hunt. You do not need to go through poison oak, but it will be around you. Not recommended for a night caching expedition.
8/13/04: Congratulations to Kablooey! Hints added below.
Just a note, since so many recent logs mention it -- originally there was no hint. The difficulty rating reflects the puzzle cache without the hint. If you want to do a true 4.5, don't read the hint. I'm not going to re-rate the cache because it's a key part of the Fizzy challenges, and I don't want to remove the puzzle hint because then the cache would not be enjoyed by as many people.
Edit 7/16/14: Cache replaced with smaller container in same location. Happy 10th anniversary to this cache!