It's a St. Johnswort for sure, however, that's the best I can do. Most of these are native but you will have to check with local experts on the pictured species. This plant is not the eurasian species that is used as an anti-depressant herb.

I did a quick search for 'yellow wildflower' and found this great site at Colo State U with 22 pages of photos. I found several that had similar flowers and several with similar leaves, but none with both that I could tell. The leaf looks like a Rosemary in your photo, but I couldn't find anything in that category. The flower looks like Helianthus, but couldn't match the leaf. It's a lovely little plant, though. Good luck with your search. Here is a link that might be useful: Yellow wildflowers at CSU

^ Aye, Sida abutifolia (Sida filicaulis/Spreading Fanpetals) looks like a good match! "A small, spreading member of the mallow family that prefers disturbed sites. Found from Texas west to California." And it's apparently native to the West Indies and South America...

Thanks, everyone. The family does grow all sorts of fruits and vegetables back there, many vining. They've built structures and trellises to support, so this rogue vine took me a bit by surprise. After last year's Passiflora incarnata debacle -- I don't think they realized what they'd planted, as it took over their (and my) yard twice, one time completely engulfing their apple tree -- I'm a bit leery when I spot something new that might end up in my yard.