I garden in a large community garden and was interested in getting into heirloom growing and seed saving. Will there be too much cross pollinating going on from my garden neighbors to have true heirlooms?
It all depends on what you plant to plant and save seeds from. And the problem isn't just from your neighbors, it has to do with what you grow yourself.
For instance, Heirloom tomato varieties can cross if blossoms aren't bagged or they aren't grown far enough apart. Different melons can cross, different cukes can cross, different squash can cross, again depending on which varieties you plant, and on and on.
I highly suggest you get a hold of a book called From Seed to Seed by Suzanne Ashworth and read up on what crosses with what and how to save seeds from the various veggies and fruits.