This is CYDISTA POTOSINA, with no good English name, so I just call it Purple Cydista, even though that name could apply to other species as well. If you're familiar with the North's Trumpet Creepers probably you can guess that Cydista is in the same family as those pretty vines, the Bignoniaceae. Features of that family include its plants bearing large, tubular flowers and opposite leaves (two arising at each stem node) and the leaves being compound. Many Bignoniaceae are vines, too. A shot into a Cydista potosina blossom is shown below:

As with Trumpet Creepers, four stamens arch upward with their anthers hugging the flower's ceiling so that pollen will be daubed onto the back of any entering pollinator. Also as with Trumpet Creepers, the stigma, the female part receiveing pollen from other flowers, is held beyond the anthers, and looks like the palms of two hands held open.

Purple Cydista's compound leaves, however, are very different from those of the North's Trumpet Creepers. Trumpet Creeper leaves bear 9-11 leaflets while Purple Cydista's have only two, its terminal leaflet being modified into an unbranching, coiling tendril, as shown below:

Two other features distinguishing Purple Cydista, visible in the last photo, are that the vine's stems are square in cross-section with fairly sharp corners, and, at least on new growth, at the base of each compound leaf's petiole, where it attaches to the stem, there are conspicuous, leafy stipules. Stipules are modified leaves that usually help protect tender, emerging new growth. Often they fall off after the new growth hardens, sometimes they stay on the stem, and in many species and plant families they don't exist at all. Cydista potosina's new stems bear stipules but the stipules fall from older stems.

Cydista potosina is one of several slender, woody vines in this area traditionally used by the Maya for weaving baskets. When I ask José the shaman about it, though, instead of talking about basket weaving he says that it's medicinal, used against "vientos malos," or "bad winds." Bad winds inflict you with various pains and ailments and are caused when you come into conflict with certain lines of energy.

Well, with José you never know where your discussion will lead when you ask a simple question about a common plant.