In case the rain took you by surprise during the promenade around Mylapore, stop by Madras Coffee House - Kapali Thottam, Mylapore. Google users granted the score of 4.1 to this place.
On my genuine opinion it's little bit costly for the small shop of size 10x10 which is on the road side as there is no seating at all unless you use the corporation small wall. You can get the same quality of coffee in Sangeetha hotel where there are proper seating available and the price remains the same. I've heard that in cotha's coffee near Mylapore temple is charging at much lesser price than this and the quality is also very good. Tomorrow I'll visit that shop and tell my genuine review.