I have read posts about strollers being stolen but I don't know how common it is.
I have a BOB stroller and couldn't travel with it since we were flying. I found a fantastic deal on Ebay on a brand new Maclaren Volo with slight staining. I added a cup holder/storage bag, seat liner, and travel bag. All together I paid about $100 which is the same cost as the travel bag for BOB. We LOVED the Volo and I'll be buying a double when #2 comes along. That said, if I were driving and had room, BOB would go to the parks with me.
I am 99.44% sure your stroller would be fine, but you can get a small bike lock for some peace of mind. Also, I am not sure if people really steal strollers or just get them confused in the chaos. Try marking your stroller with something you can see easily at a distance, like a bright bandana or the balloon the kids just have to have. This will help you find it in the massive stroller parking areas and will keep others from getting confused.
Have a great time!