If you can& decide what to plant in that protected, semishady corner, you can& go wrong with tuberous begonia. Keeping the plant alive and healthy requires some extra attention, but this article can help with that.
How To Overwinter Sweet Potato Vine Cuttings Indoors
Mandevilla plants in winter survive the season in fine shape if you live in a tropical climate. However, if you live in a more northern climate, planting the vine in a container is the best way to go. Read this article for info on winterizing mandevillas.