Although this might seem to be a straightforward question, the first thing that you have to determine is whether your walls are really stucco or if they're synthetic stucco known as EIFS (Exterior Insulation Finishing System). EIFS is an acrylic-based product that is applied over foam insulation, whereas real stucco is a mixture of Portland cement and sand that hardens to rocklike strength when dry. If what you have is real stucco and you want to use a saber saw blade to cut it, make sure the blade is a carbide one. Alternatively, you could drill holes with a masonry drill bit and then use a metal-cutting blade on your saber saw to cut a line from one hole to the next hole.
All of the above assumes that you're cutting the stucco to make some sort of repair or to add something to the wall. However, if you're cutting the stucco because you want to demolish the wall, it's a waste of time to use a saber saw blade. You're probably better off with an electric chipping hammer.