Most good elastomeric paints don't require priming over clean sound stucco. A good manufacture in California is Kelly-Moore. Kelly-Moore's 1128 Smooth Elastomeric Coating is very good. I recommend two coats of the paint for a pin hole free surface.
Priming is recommended if the stucco has excessive efflorescence deposits or if previously painted and this coating is failing. I highly recommend pressure washing before painting stucco and follow all of the needed preparation steps. <a href="https://www.house-painting-info.com/stucco.html">Check out Painting Stucco for more information</a>.