From this site with other helpful info:
Since 45 to 50 °
F is the minimum temperature that can be tolerated by mandevilla, plants should be moved indoors for the winter. Before bringing them indoors, examine them carefully for pests. Look under the leaves, in the leaf axils, and in every conceivable nook and cranny for insects and their eggs. Remove any diseased or dead leaves by hand. Insect-infested plants can be doused with a forceful spray of water to dislodge the pests, or you can use insecticidal soaps or other appropriate insecticides labelled for use on your plant. You may have to prune some of the plant to compensate for any root loss. Move the plants to a well-lit location where the temperature is above 45 to 50 °
F. Reduce the frequency of watering to coincide with the plants’ rest periods induced by the cooler temperatures and reduced light.
In late winter or early spring before growth begins, prune by removing old, crowded stems and shortening others. Even if mandevilla is pruned almost to the ground, it will bloom the same summer on the new shoots, which develop from the base of the plants.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.