My family and I (2 adults, 2 toddlers ages 4 and 2) spent 4 nites at the Residence Inn-Mission Bay based on the reviews I read on Tripadvisor.
My first impression was that the hotel and our room was clean, bright and new. Our room was a 2 bedroom king with a kid's suite. The website advertises the kid's suite with bunk beds, but ours came with two separate twin beds. This actually worked out better since our children were probably too young for a bunk bed setup.
The kitchen was well stocked with utensils and dishware. The stove top was missing the knobs for the burners. We didn't use the stove so it wasn't an issue (I assumed the knobs were somewhere in the drawers). The living area and masterbed room and bathroom were comfortable and again clean--which being new parents with toddlers was a great concern and major consideration on choosing a hotel for our first summer vacation.
The second concern I had was how quiet the rooms are at nite--I'm a light sleeper and having 2 toddlers getting woken up by noise means no one would get any sleep. Luckily, even though you can definitely hear loud voices or pitter patter or feet running around, I think that since most of the guests were families traveling with kids there was hardly any commotion I hear after 10 or 11 o'clock when families are probably passed out.
The hotel had a toddler pool (1 foot deep, ~10ft diameter), a main pool and a spa. We didn't use the hotel pool, but many guests did. The laundry facilities were modern which even uses low water front loader washing machines. The gameroom had pool tables, air hockey, foosball and few arcade games. There was a second gameroom which was small and not well air conditioned that had some older arcade games.
The best features of the hotel were the complimentary hot buffet breakfast and the evening "dinner". The breakfast always had hot eggs (one basic scrambled and the other a variation like hame and cheese or spinach and mushroom etc), sausage or bacon, hot potatoes or beans, oatmeal, pancakes/waffles, several types of cereals and breads and variety of hot and cold drinks (milk, juice, coffee). The selection was great. At nite, the hotel had things like bbq hot dogs and hamburgers or spaghetti and meatballs. The dinners weren't 5 course meals, but great for something quick after a long day at Sea World or the Zoo and you can relax and eat by the pool.
Overall the Residence Inn met my expectations on cleanliness, amenities, and staff professionalism. The only negative I can think of is that the buffet breakfasts can be crowded (I heard the weekends can be crazy) but the staff did a good job keeping up during our stay. I would definitely recommend this hotel to other families and would stay here again.

It's your typical Marriott Residence Inn, modern, tastefully decorated, clean, two room suite, kitchen, etc. Nice breakfast (despite the icky powdered eggs) well-stocked with plenty of seating and lots of food. Very kid-oriented with a cartoon area in the breakfast room, game room, kid floaties in the pool. Pool was packed with kids. In fact, all the guests seemed to be families with kids of all ages (uh, including us). Of course, there was the couple that came out of the elevator with six huge dogs on leashes...so I guess it's a dog-friendly place too.

Staff seemed fine...those working on refilling the free breakfast buffet seemed to be working very hard. Front desk kindly printed driving instructions on how to get to the zoo, and then back to the hotel.

The hotel layout is absolutely confusing...one part has four stories, the other part five, elevators and exits everywhere and once inside the building we seemed to completely lose all sense of direction.

Having to pay for parking is appalling...though typical of most San Diego hotels, this is particularly galling at this establishment because there is no where else to park except for the parking lot (gated, with access by using your room card).

Hotel Circle is a dismal freeway frontage road of chain hotels and motels. Not the sort of place you'd want to take an evening stroll. We had to drive to find someplace to eat and stumbled upon a satisfying King's Seafood in a nearby strip mall. True, there was a place called Ricky's, an older diner about a five to ten minute walk from the hotel. We had to walk past a fenced-in, boarded-up, failed spa business, and overgrown weed-filled, vacant lots filled with trash and empty liquor bottles to get there.

We stayed for two nights because my husband was attending a conference at a nearby hotel. The location, despite being dismal, is a short drive to Balboa Park, Old Town, etc. It took about ten minutes to get to the zoo via the nearby freeway. Still, Hotel Circle is pretty soulless, and well, depressing. The hotel itself was fine.

My family of 6 stayed here 5 nights as part of our San Diego trip and we could not have been more pleased. To keep things short, here's the summary....

-clean rooms with plenty of space and full kitchens
-super quiet
-friendly, efficient, helpful staff
-great breakfast with some daily variety
-super clean pool, hot tu, and kids play pool
-nice evening reception (M-Th)
-feeling of security
-less than 15 minutes to almost everything
-easy on/off highway

We usually stay at ES, but this place was awesome! As they say in SoCal, "No worries."

The location of this hotel is "off the highway" which after driving two hours from Anaheim, made me a little nervous. But on the plus side of its location, it is very close (10 mins. or less) to Historic San Diego (not the Gaslamp Dist.) and of course highway access is a breeze. It is set pretty far back from road and noise or activity level were never an issue.
Okay - we were put in a Handicap room (seemingly because we arrived in the late afternoon). The room seemed to be smaller than other Res. Inns. The interior is dated and a little worn. The shower is NOT one of those wall-less handicap showers that lets water go everywhere though. There is no closed closet - no bigg-y. And the volume on the dated TV's is picky.
The breakfast is a free-for-all. It was so busy but they have a sign that indicates that they restock btwn. 9:15 - 9:30. And they do. It has what you would expect - powder eggs, fruit, oatmeal, breads, drinks, etc.
We paid more for this hotel for two nights that we did for four nights at a Marriott Suites in Anaheim. (We got a screamin' deal there). Admittedly we were not there for its ammenities and again the location (convenience wise) couldn't be beat. But it's too bad they can't put a little money towards making it a slightly nicer retreat for travel, park weary families.