@needrain, I don't know if this will help or even if it is still true. So many things have changed in the plant world since I kept this info from GW or DG
Allamandas can be grown as container plants on a support system, as a hanging basket trailing plant or in warmer climates as an inground plant. They can get leggy and they like to sprawl. Our plants in Sebring took over a 12 foot fence and grew 9 feet tall. I was always pruning them and they kept bushing and growing. They will tolerate temperatures down to around 25 F but will generally come back from a freeze. They are more of a shrub type plant than a vine.
Botanically Dipladenia and Mandevilla are the same but there is a difference in Dipladenia or mandevilla sanderii. The former are generally large leaved vines that have large trumpet flowers and the predominant color is a very deep fushia or red color. There are some different cultivars in varying shades. The latter is somewhat different as the leaves are much smaller and they do not tend to climb. They are used more as container or semi-hanging basket plants. They do not do too well inground and prefer to remain containerized. If you are looking for a vine then you wish to go with the true mandevilla. I have a unique varigated leaf with light lavender flowers. They do not like cold weather too much but will grow up and up. The Dipladenia are extremely happy with beachfront conditions. Neither like cold wet feet in the winter and they make it the first year but will die the second
