We stayed at Lawrence for one night in August, and we payed 850 Rupees for a double room including breakfast (tea/coffee, toast with butter and jam, and a banana). It was well worth the cost, definitely the best value for money in Mumbai. The staff was very nice and they let us check in early and leave our bag in their office until our train left, which was 10+ hours after check out time. The rooms are very basic but clean. They are also very airy because of the big windows and fan. The manager has an electrical outlet in his office for charging phones/cameras.
It's very easy to find, just tell the cab driver Rhythm House (music store), Kala Ghoda (the area, pronounced 'Kala Gooda'). If you walk up the street on the left side of Rhythm House you will see a blue synagogue on the right, turn right into the street in front of the synagogue. Walk a couple of meters and you will see the Hotel Lawrence sign on a building on the left side of the road. there is a book store next to the entrance.
The hotel is walking distance from Marine drive, Eros cinema and Colaba. Very nice location.