Dude, what are you looking to do with the bamboo? Make a hedge or visual screen?

Kt

You can get bamboo on craigslist and it'll be vastly cheaper than at a garden center.

Figure out what you want first though, don't just get any-old bamboo you run into. The most common ones tend to be the most invasive.

If you don't mind going out of town, try Bamboo Sourcery in Sebastopol:
http://www.bamboosourcery.com/
or Cactus Jungle in Berkeley:
http://www.bamboosfbayarea.com/
In San Francisco the best place is the monthly sales at Strybing Arboretum:
http://www.sfbotanicalgarden.org/plant_sales/plant_sales.htm
The next sale is Feb 6. I'm a volunteer there and grow the bamboo.

Bamboo Sourcery is a rip off. High prices and so-so quality. In a urban environment, stick with clumpers. For tall hedges go with Oldhamii, for medium hedge go with Alphonse Karr.

American Bamboo Society web site has Species Tables where basic traits can be seen at a glance, local suppliers identified.