June 2019 update:
I have re positioned this plant in May, in a more filtered light area, closer to the house. It gets western sun in the afternoon so that is quite hot, but thanks to the canopy of city trees, it is not getting roasted dry. I have also been watering this everyday, with special attention to misting the vine.
I guess I was underwatering it too much before. With the correction on watering, it held on to the leaves. Usually during summer it has dropped it all, and the vine is just like a dried out twig. This time around it is different. I guess being a young plant it really likes frequent watering. It is quite slow growing, caudex not any bigger, but it is remaining rock solid, so that reassures me. Hard to overwater at this time with our very dry and hot environment.