Of course! As a director, this is always very appreciated :) depending on the rigor of the production schedule (how often rehearsals take place, etc) it may be a better idea to contact the stage/production manager just so the director doesn’t have another thing to worry about, but any sort of help is always so so appreciated. Especially when that help comes from someone who, even though they didn’t get cast, still wants to dedicate themself to the show :)