I've had similar experiences on the Beltline Trail near me. It's ridiculous some days -- I slow down, I give a warning, and the dog owners ignore me and their dogs while I play dodge 'em with their pooches. Last summer I struck a big dog as I rode into the park and I felt awful but he ran in front of me seemingly out of no where. I fell off my bike and the owner apologized to me because the area we were in is on-leash and her dog definitely was running free. As I got back on my bike the same dog dove in front of me again. Irritating as hell.