When I dropped by Davao City last month from my Isulan trip, my Davao-based friend, Mae, chose and booked a place for me to stay there. 
I was quite happy with her choice. Frances Inn is located along Quimpo Boulevard; it’s walking distance from the bus station (Davao Ecoland Terminal) and easily accessible by jeepney and taxi. Should you fly in the city, the place is also a smooth ride from and to the airport. I found the place clean with good amenities including cable TV in all rooms (they have LCD TV with remote), hot and cold shower and they also have great Wi-fi! Although they do not serve complimentary breakfast with your stay, you could get delicious and affordable food from their dining area/restaurant.
One thing that I just thought I needed more in my room is a small table to put some of my stuff on. My room (a semi double one) , had a closet and a nice dresser but I missed having another table in the room. But other than this, the place was good enough for me.
Rates start from P700 (about 18 USD) for a single room; a suite room is at P1800 (about 47 USD).
Below are a couple of shots. Unfortunately, my shots of the room did not come out well so I could not post them here.