The Hotel Circle area and Mission Valley/Fashion Valley have a TON of great restaurants that would be very close for you to take a cab to. I looked at a map and it appears that Days Inn is across the freeway from Fashion Valley, so you wouldn't really be able to walk, but at the Fashion Valley mall, there is a Cheesecake Factory and P.F. Chang's.
Down the road just a couple of minutes is Mission Valley, which has Gordon Biersch (brewery and restaurant), Seau's, Bennigan's, King's Fish House, and a lot more.
You will also be pretty close to Old Town San Diego, which is definitely worth spending some time in - to walk around, do some shopping, and eat at any of the great restaurants there.
SeaWorld is really not far at all from there.
Have a great time!