Only stay here if you have a pet or if you have to cook.
There are actually 2 Extended Stay America Hotels in Mission Valley, San Diego. This one is on 7444 Mission Valley Road (previously called Homestead Suites), and the other one is on 3860 Murphy Canyon Road. If possible, you should stay in the other one, which is currently ranked 100 spots higher than this one, or maybe you would be better off staying in a completely different hotel chain. The other Extended Stay America Hotel on 3860 Murphy Canyon Road has just been remodeled and has all interior hallways. I know this because I accidentally drove to the wrong hotel.
This hotel on 7444 Mission Valley Road is decent. Don't expect any frills. It has the usual kitchenette with stove, refrigerator, microwave, and coffee maker. The king bed is okay. The sofa bed is uncomfortable. You can feel every spring in the sofa bed mattress. There are outdoor hallways, which means it's loud. There's no housekeeping unless you are staying for 7+ days. Free Wifi. Free parking. Loud A/C. Windows are only open to the hallway, so don't expect any privacy. Rooms are old and show signs of age.
It's located approximately 2 miles from Old Town San Diego which is convenient. Unfortunately, it's also in the back of a business area with nothing within walking distance. 
I guess the only reasons to stay here would be if you have a pet or if you have to cook.