There are lots of options if you have got interest in Plays and Monologues. Delhi has a rich and flourishing theatre culture and some of the best actors in the Hindi Film Industry have theatre background. Kamani Auditorium, FICCI Auditorium and National School of Dramas are the major place to catch latest of English or vernacular plays. Kamani Auditorium situated at Mandi house is in a way center for all the cultural activities in Delhi. Most of the time there is free entry but at times you need to have invitation to attend functions.
Besides you have National School of Drama in the vicinity that is a premiere institute for the budding actors. Plays, both Hindi/Urdu and English, are organized regularly and tickets are very nominal, 1$ or less in most of the cases. You have other places too such as FICCI auditorium and Siri Fort Auditorium which regularly organizes plays and cultural activities.