A special thanks to all the GREAT folks over at Gardenweb's Fruit and Orchards Forum, particularly Murky, Austransplant, Fruitgirl, Jellyman and Cambse! I learned tons from all of you.
The best information I got was the fact that the variety of blackberry bush is a Himalayan, which is essentially an invasive weed that does indeed grow over my fence every year. It doesn't impact my garden though, as it is on the other side of the yard from my garden. They'd just kill my pear tree in half a second. We actually hack back a 2-3 foot path away from my fence every year after harvesting. Great information. Now I just need to find a hedge trimmer. Nobody in my family has one of those, but I can see how it'd come in handy.
Also, I learned that there are many varieties of blackberries that don't have thorns. Wouldn't that be nice if wasn't working on city property. hehe.
I just love blackberry jelly. It's hard to make (get all those seeds out) but it's worth it. It goes very well with the plum jelly we make from the plums from my tree, and the pears make great canned pears (on cottage cheese, yum!). Hehe, my wife scolded me today for saying that all we needed were the jellies we make from our own harvest. She loves a good strawberry jam as much as I do. Maybe someday I'll plant strawberries, but I don't think we'll ever have a strawberry harvest to make tons of jam. She suggests we just go to a U-Pick farm and get a handful of flats.
Anyway, it sounds like I've got a good topic to talk to my neighbor about next time I see him. Thanks all!