It looks like one to me - can't name it, but if you'll post your picture on the 'Passifloras' forum, someone will i.d. it for you!

It might be a corkystem passiflora. I have a what I thought was an unlobed suberosa that I was told is actually a P. pallida that looks very similar to your vines. See if the older part of the stem begins to grow a thick white covering. If it does I'd bet that's what it is. I found it growing all over the place in S. FL.